diff --git a/src/AddressBook/ABAddressBook.cs b/src/AddressBook/ABAddressBook.cs
index f94b02665e..5c36dd5925 100644
--- a/src/AddressBook/ABAddressBook.cs
+++ b/src/AddressBook/ABAddressBook.cs
@@ -170,7 +170,7 @@ namespace AddressBook {
 
 		static ABAddressBook ()
 		{
-			ErrorDomain = Dlfcn.GetStringConstant (Libraries.AddressBook.Handle, "ABAddressBookErrorDomain");
+			ErrorDomain = Dlfcn.GetStringConstant (Libraries.AddressBook.Handle, "ABAddressBookErrorDomain")!;
 		}
 
 		protected override void Dispose (bool disposing)
diff --git a/src/CoreText/CTFontCollection.cs b/src/CoreText/CTFontCollection.cs
index 9add137520..0c6a3190d9 100644
--- a/src/CoreText/CTFontCollection.cs
+++ b/src/CoreText/CTFontCollection.cs
@@ -47,7 +47,7 @@ namespace CoreText {
 
 		static CTFontCollectionOptionKey ()
 		{
-			RemoveDuplicates = Dlfcn.GetStringConstant (Libraries.CoreText.Handle, "kCTFontCollectionRemoveDuplicatesOption");
+			RemoveDuplicates = Dlfcn.GetStringConstant (Libraries.CoreText.Handle, "kCTFontCollectionRemoveDuplicatesOption")!;
 		}
 	}
 
diff --git a/src/CoreText/CTFontDescriptor.cs b/src/CoreText/CTFontDescriptor.cs
index f56aacb96a..13cdabdbef 100644
--- a/src/CoreText/CTFontDescriptor.cs
+++ b/src/CoreText/CTFontDescriptor.cs
@@ -110,28 +110,28 @@ namespace CoreText {
 		static CTFontDescriptorAttributeKey ()
 		{
 			var handle = Libraries.CoreText.Handle;
-			Url                 = Dlfcn.GetStringConstant (handle, "kCTFontURLAttribute");
-			Name                = Dlfcn.GetStringConstant (handle, "kCTFontNameAttribute");
-			DisplayName         = Dlfcn.GetStringConstant (handle, "kCTFontDisplayNameAttribute");
-			FamilyName          = Dlfcn.GetStringConstant (handle, "kCTFontFamilyNameAttribute");
-			StyleName           = Dlfcn.GetStringConstant (handle, "kCTFontStyleNameAttribute");
-			Traits              = Dlfcn.GetStringConstant (handle, "kCTFontTraitsAttribute");
-			Variation           = Dlfcn.GetStringConstant (handle, "kCTFontVariationAttribute");
-			Size                = Dlfcn.GetStringConstant (handle, "kCTFontSizeAttribute");
-			Matrix              = Dlfcn.GetStringConstant (handle, "kCTFontMatrixAttribute");
-			CascadeList         = Dlfcn.GetStringConstant (handle, "kCTFontCascadeListAttribute");
-			CharacterSet        = Dlfcn.GetStringConstant (handle, "kCTFontCharacterSetAttribute");
-			Languages           = Dlfcn.GetStringConstant (handle, "kCTFontLanguagesAttribute");
-			BaselineAdjust      = Dlfcn.GetStringConstant (handle, "kCTFontBaselineAdjustAttribute");
-			MacintoshEncodings  = Dlfcn.GetStringConstant (handle, "kCTFontMacintoshEncodingsAttribute");
-			Features            = Dlfcn.GetStringConstant (handle, "kCTFontFeaturesAttribute");
-			FeatureSettings     = Dlfcn.GetStringConstant (handle, "kCTFontFeatureSettingsAttribute");
-			FixedAdvance        = Dlfcn.GetStringConstant (handle, "kCTFontFixedAdvanceAttribute");
-			FontOrientation     = Dlfcn.GetStringConstant (handle, "kCTFontOrientationAttribute");
-			FontFormat          = Dlfcn.GetStringConstant (handle, "kCTFontFormatAttribute");
-			RegistrationScope   = Dlfcn.GetStringConstant (handle, "kCTFontRegistrationScopeAttribute");
-			Priority            = Dlfcn.GetStringConstant (handle, "kCTFontPriorityAttribute");
-			Enabled             = Dlfcn.GetStringConstant (handle, "kCTFontEnabledAttribute");
+			Url                 = Dlfcn.GetStringConstant (handle, "kCTFontURLAttribute")!;
+			Name                = Dlfcn.GetStringConstant (handle, "kCTFontNameAttribute")!;
+			DisplayName         = Dlfcn.GetStringConstant (handle, "kCTFontDisplayNameAttribute")!;
+			FamilyName          = Dlfcn.GetStringConstant (handle, "kCTFontFamilyNameAttribute")!;
+			StyleName           = Dlfcn.GetStringConstant (handle, "kCTFontStyleNameAttribute")!;
+			Traits              = Dlfcn.GetStringConstant (handle, "kCTFontTraitsAttribute")!;
+			Variation           = Dlfcn.GetStringConstant (handle, "kCTFontVariationAttribute")!;
+			Size                = Dlfcn.GetStringConstant (handle, "kCTFontSizeAttribute")!;
+			Matrix              = Dlfcn.GetStringConstant (handle, "kCTFontMatrixAttribute")!;
+			CascadeList         = Dlfcn.GetStringConstant (handle, "kCTFontCascadeListAttribute")!;
+			CharacterSet        = Dlfcn.GetStringConstant (handle, "kCTFontCharacterSetAttribute")!;
+			Languages           = Dlfcn.GetStringConstant (handle, "kCTFontLanguagesAttribute")!;
+			BaselineAdjust      = Dlfcn.GetStringConstant (handle, "kCTFontBaselineAdjustAttribute")!;
+			MacintoshEncodings  = Dlfcn.GetStringConstant (handle, "kCTFontMacintoshEncodingsAttribute")!;
+			Features            = Dlfcn.GetStringConstant (handle, "kCTFontFeaturesAttribute")!;
+			FeatureSettings     = Dlfcn.GetStringConstant (handle, "kCTFontFeatureSettingsAttribute")!;
+			FixedAdvance        = Dlfcn.GetStringConstant (handle, "kCTFontFixedAdvanceAttribute")!;
+			FontOrientation     = Dlfcn.GetStringConstant (handle, "kCTFontOrientationAttribute")!;
+			FontFormat          = Dlfcn.GetStringConstant (handle, "kCTFontFormatAttribute")!;
+			RegistrationScope   = Dlfcn.GetStringConstant (handle, "kCTFontRegistrationScopeAttribute")!;
+			Priority            = Dlfcn.GetStringConstant (handle, "kCTFontPriorityAttribute")!;
+			Enabled             = Dlfcn.GetStringConstant (handle, "kCTFontEnabledAttribute")!;
 		}
 	}
 
diff --git a/src/CoreText/CTFrame.cs b/src/CoreText/CTFrame.cs
index 7096fedfc8..dbcec78b4a 100644
--- a/src/CoreText/CTFrame.cs
+++ b/src/CoreText/CTFrame.cs
@@ -62,11 +62,11 @@ namespace CoreText {
 		static CTFrameAttributeKey ()
 		{
 			var handle = Libraries.CoreText.Handle;
-			Progression = Dlfcn.GetStringConstant (handle, "kCTFrameProgressionAttributeName");
-			PathFillRule = Dlfcn.GetStringConstant (handle, "kCTFramePathFillRuleAttributeName");
-			PathWidth = Dlfcn.GetStringConstant (handle, "kCTFramePathWidthAttributeName");
-			ClippingPaths = Dlfcn.GetStringConstant (handle, "kCTFrameClippingPathsAttributeName");
-			PathClippingPath = Dlfcn.GetStringConstant (handle, "kCTFramePathClippingPathAttributeName");
+			Progression = Dlfcn.GetStringConstant (handle, "kCTFrameProgressionAttributeName")!;
+			PathFillRule = Dlfcn.GetStringConstant (handle, "kCTFramePathFillRuleAttributeName")!;
+			PathWidth = Dlfcn.GetStringConstant (handle, "kCTFramePathWidthAttributeName")!;
+			ClippingPaths = Dlfcn.GetStringConstant (handle, "kCTFrameClippingPathsAttributeName")!;
+			PathClippingPath = Dlfcn.GetStringConstant (handle, "kCTFramePathClippingPathAttributeName")!;
 		}
 	}
 
diff --git a/src/CoreText/CTTextTab.cs b/src/CoreText/CTTextTab.cs
index 2406e40c88..8fb839210b 100644
--- a/src/CoreText/CTTextTab.cs
+++ b/src/CoreText/CTTextTab.cs
@@ -43,7 +43,7 @@ namespace CoreText {
 
 		static CTTextTabOptionKey ()
 		{
-			ColumnTerminators = Dlfcn.GetStringConstant (Libraries.CoreText.Handle, "kCTTabColumnTerminatorsAttributeName");
+			ColumnTerminators = Dlfcn.GetStringConstant (Libraries.CoreText.Handle, "kCTTabColumnTerminatorsAttributeName")!;
 		}
 	}
 
diff --git a/src/CoreVideo/CVPixelFormatDescription.cs b/src/CoreVideo/CVPixelFormatDescription.cs
index 07ee3e6e6c..a404355741 100644
--- a/src/CoreVideo/CVPixelFormatDescription.cs
+++ b/src/CoreVideo/CVPixelFormatDescription.cs
@@ -105,41 +105,41 @@ namespace CoreVideo {
 		static CVPixelFormatDescription ()
 		{
 			var handle = Libraries.CoreVideo.Handle;
-			NameKey = Dlfcn.GetStringConstant (handle, "kCVPixelFormatName");
-			ConstantKey = Dlfcn.GetStringConstant (handle, "kCVPixelFormatConstant");
-			CodecTypeKey = Dlfcn.GetStringConstant (handle, "kCVPixelFormatCodecType");
-			FourCCKey = Dlfcn.GetStringConstant (handle, "kCVPixelFormatFourCC");
-			PlanesKey = Dlfcn.GetStringConstant (handle, "kCVPixelFormatPlanes");
-			BlockWidthKey = Dlfcn.GetStringConstant (handle, "kCVPixelFormatBlockWidth");
-			BlockHeightKey = Dlfcn.GetStringConstant (handle, "kCVPixelFormatBlockHeight");
-			BitsPerBlockKey = Dlfcn.GetStringConstant (handle, "kCVPixelFormatBitsPerBlock");
-			BlockHorizontalAlignmentKey = Dlfcn.GetStringConstant (handle, "kCVPixelFormatBlockHorizontalAlignment");
-			BlockVerticalAlignmentKey = Dlfcn.GetStringConstant (handle, "kCVPixelFormatBlockVerticalAlignment");
-			BlackBlockKey = Dlfcn.GetStringConstant (handle, "kCVPixelFormatBlackBlock");
-			HorizontalSubsamplingKey = Dlfcn.GetStringConstant (handle, "kCVPixelFormatHorizontalSubsampling");
-			VerticalSubsamplingKey = Dlfcn.GetStringConstant (handle, "kCVPixelFormatVerticalSubsampling");
-			OpenGLFormatKey = Dlfcn.GetStringConstant (handle, "kCVPixelFormatOpenGLFormat");
-			OpenGLTypeKey = Dlfcn.GetStringConstant (handle, "kCVPixelFormatOpenGLType");
-			OpenGLInternalFormatKey = Dlfcn.GetStringConstant (handle, "kCVPixelFormatOpenGLInternalFormat");
-			CGBitmapInfoKey = Dlfcn.GetStringConstant (handle, "kCVPixelFormatCGBitmapInfo");
-			QDCompatibilityKey = Dlfcn.GetStringConstant (handle, "kCVPixelFormatQDCompatibility");
-			CGBitmapContextCompatibilityKey = Dlfcn.GetStringConstant (handle, "kCVPixelFormatCGBitmapContextCompatibility");
-			CGImageCompatibilityKey = Dlfcn.GetStringConstant (handle, "kCVPixelFormatCGImageCompatibility");
-			OpenGLCompatibilityKey = Dlfcn.GetStringConstant (handle, "kCVPixelFormatOpenGLCompatibility");
-			FillExtendedPixelsCallbackKey = Dlfcn.GetStringConstant (handle, "kCVPixelFormatFillExtendedPixelsCallback");
+			NameKey = Dlfcn.GetStringConstant (handle, "kCVPixelFormatName")!;
+			ConstantKey = Dlfcn.GetStringConstant (handle, "kCVPixelFormatConstant")!;
+			CodecTypeKey = Dlfcn.GetStringConstant (handle, "kCVPixelFormatCodecType")!;
+			FourCCKey = Dlfcn.GetStringConstant (handle, "kCVPixelFormatFourCC")!;
+			PlanesKey = Dlfcn.GetStringConstant (handle, "kCVPixelFormatPlanes")!;
+			BlockWidthKey = Dlfcn.GetStringConstant (handle, "kCVPixelFormatBlockWidth")!;
+			BlockHeightKey = Dlfcn.GetStringConstant (handle, "kCVPixelFormatBlockHeight")!;
+			BitsPerBlockKey = Dlfcn.GetStringConstant (handle, "kCVPixelFormatBitsPerBlock")!;
+			BlockHorizontalAlignmentKey = Dlfcn.GetStringConstant (handle, "kCVPixelFormatBlockHorizontalAlignment")!;
+			BlockVerticalAlignmentKey = Dlfcn.GetStringConstant (handle, "kCVPixelFormatBlockVerticalAlignment")!;
+			BlackBlockKey = Dlfcn.GetStringConstant (handle, "kCVPixelFormatBlackBlock")!;
+			HorizontalSubsamplingKey = Dlfcn.GetStringConstant (handle, "kCVPixelFormatHorizontalSubsampling")!;
+			VerticalSubsamplingKey = Dlfcn.GetStringConstant (handle, "kCVPixelFormatVerticalSubsampling")!;
+			OpenGLFormatKey = Dlfcn.GetStringConstant (handle, "kCVPixelFormatOpenGLFormat")!;
+			OpenGLTypeKey = Dlfcn.GetStringConstant (handle, "kCVPixelFormatOpenGLType")!;
+			OpenGLInternalFormatKey = Dlfcn.GetStringConstant (handle, "kCVPixelFormatOpenGLInternalFormat")!;
+			CGBitmapInfoKey = Dlfcn.GetStringConstant (handle, "kCVPixelFormatCGBitmapInfo")!;
+			QDCompatibilityKey = Dlfcn.GetStringConstant (handle, "kCVPixelFormatQDCompatibility")!;
+			CGBitmapContextCompatibilityKey = Dlfcn.GetStringConstant (handle, "kCVPixelFormatCGBitmapContextCompatibility")!;
+			CGImageCompatibilityKey = Dlfcn.GetStringConstant (handle, "kCVPixelFormatCGImageCompatibility")!;
+			OpenGLCompatibilityKey = Dlfcn.GetStringConstant (handle, "kCVPixelFormatOpenGLCompatibility")!;
+			FillExtendedPixelsCallbackKey = Dlfcn.GetStringConstant (handle, "kCVPixelFormatFillExtendedPixelsCallback")!;
 
 			//iOS8 only
-			ContainsRgb = Dlfcn.GetStringConstant (handle, "kCVPixelFormatContainsRGB");
-			ContainsYCbCr = Dlfcn.GetStringConstant (handle, "kCVPixelFormatContainsYCbCr");
+			ContainsRgb = Dlfcn.GetStringConstant (handle, "kCVPixelFormatContainsRGB")!;
+			ContainsYCbCr = Dlfcn.GetStringConstant (handle, "kCVPixelFormatContainsYCbCr")!;
 
 			//iOS9 only
-			ComponentRangeKey = Dlfcn.GetStringConstant (handle, "kCVPixelFormatComponentRange");
-			ComponentRangeFullRangeKey = Dlfcn.GetStringConstant (handle, "kCVPixelFormatComponentRange_FullRange");
-			ComponentRangeVideoRangeKey = Dlfcn.GetStringConstant (handle, "kCVPixelFormatComponentRange_VideoRange");
-			ComponentRangeWideRangeKey = Dlfcn.GetStringConstant (handle, "kCVPixelFormatComponentRange_WideRange");
+			ComponentRangeKey = Dlfcn.GetStringConstant (handle, "kCVPixelFormatComponentRange")!;
+			ComponentRangeFullRangeKey = Dlfcn.GetStringConstant (handle, "kCVPixelFormatComponentRange_FullRange")!;
+			ComponentRangeVideoRangeKey = Dlfcn.GetStringConstant (handle, "kCVPixelFormatComponentRange_VideoRange")!;
+			ComponentRangeWideRangeKey = Dlfcn.GetStringConstant (handle, "kCVPixelFormatComponentRange_WideRange")!;
 
 			// Xcode 10
-			ContainsGrayscaleKey = Dlfcn.GetStringConstant (handle, "kCVPixelFormatContainsGrayscale");
+			ContainsGrayscaleKey = Dlfcn.GetStringConstant (handle, "kCVPixelFormatContainsGrayscale")!;
 		}
 
 		// note: bad documentation, ref: https://bugzilla.xamarin.com/show_bug.cgi?id=13917
diff --git a/src/ObjCRuntime/Dlfcn.cs b/src/ObjCRuntime/Dlfcn.cs
index 449c573acf..252159a520 100644
--- a/src/ObjCRuntime/Dlfcn.cs
+++ b/src/ObjCRuntime/Dlfcn.cs
@@ -28,6 +28,9 @@
 // WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
 //
 //
+
+#nullable enable
+
 using System;
 using System.ComponentModel;
 using System.Runtime.InteropServices;
@@ -94,9 +97,9 @@ namespace ObjCRuntime {
 		public static extern int dlclose (IntPtr handle);
 
 		[DllImport (Constants.libSystemLibrary, EntryPoint="dlopen")]
-		internal static extern IntPtr _dlopen (string path, int mode /* this is int32, not nint */);
+		internal static extern IntPtr _dlopen (string? path, int mode /* this is int32, not nint */);
 
-		public static IntPtr dlopen (string path, int mode)
+		public static IntPtr dlopen (string? path, int mode)
 		{
 			return dlopen (path, mode, showWarning: true);
 		}
@@ -110,7 +113,7 @@ namespace ObjCRuntime {
 			warningShown = true;
 		}
 
-		internal static IntPtr dlopen (string path, int mode, bool showWarning)
+		internal static IntPtr dlopen (string? path, int mode, bool showWarning)
 		{
 			var x = _dlopen (path, mode);
 			if (x != IntPtr.Zero)
@@ -119,7 +122,7 @@ namespace ObjCRuntime {
 			// In iOS < 9, you could dlopen ("libc") and that would work.
 			// In iOS >= 9, this fails with:
 			// "no cache image with name (<top>)"
-			if (path.IndexOf ('/') == -1){
+			if (path?.IndexOf ('/') == -1){
 				if (showWarning)
 					WarnOnce ();
 				return dlopen ("/usr/lib/" + path, mode, false);
@@ -138,13 +141,13 @@ namespace ObjCRuntime {
 		[DllImport (Constants.libSystemLibrary, EntryPoint="dlerror")]
 		internal static extern IntPtr dlerror_ ();
 
-		public static string dlerror ()
+		public static string? dlerror ()
 		{
 			// we can't free the string returned from dlerror
 			return Marshal.PtrToStringAnsi (dlerror_ ());
 		}
 
-		public static NSString GetStringConstant (IntPtr handle, string symbol)
+		public static NSString? GetStringConstant (IntPtr handle, string symbol)
 		{
 			var indirect = dlsym (handle, symbol);
 			if (indirect == IntPtr.Zero)
@@ -152,7 +155,7 @@ namespace ObjCRuntime {
 			var actual = Marshal.ReadIntPtr (indirect);
 			if (actual == IntPtr.Zero)
 				return null;
-			return (NSString) Runtime.GetNSObject (actual);
+			return Runtime.GetNSObject<NSString> (actual);
 		}
 
 		public static IntPtr GetIndirect (IntPtr handle, string symbol)
@@ -160,7 +163,7 @@ namespace ObjCRuntime {
 			return dlsym (handle, symbol);
 		}
 
-		public static NSNumber GetNSNumber (IntPtr handle, string symbol)
+		public static NSNumber? GetNSNumber (IntPtr handle, string symbol)
 		{
 			var indirect = dlsym (handle, symbol);
 			if (indirect == IntPtr.Zero)
@@ -168,7 +171,7 @@ namespace ObjCRuntime {
 			var actual = Marshal.ReadIntPtr (indirect);
 			if (actual == IntPtr.Zero)
 				return null;
-			return (NSNumber) Runtime.GetNSObject (actual);
+			return Runtime.GetNSObject<NSNumber> (actual);
 		}
 
 		public static int GetInt32 (IntPtr handle, string symbol)
@@ -228,7 +231,7 @@ namespace ObjCRuntime {
 			return (ulong) Marshal.ReadInt64 (indirect);
 		}
 
-#if !XAMCORE_4_0
+#if !NET
 		[Obsolete ("Use 'SetInt64' for long values instead.")]
 		public static void SetUInt64 (IntPtr handle, string symbol, long value)
 		{
@@ -249,31 +252,31 @@ namespace ObjCRuntime {
 			Marshal.WriteInt64 (indirect, (long) value);
 		}
 
-		public static void SetString (IntPtr handle, string symbol, string value)
+		public static void SetString (IntPtr handle, string symbol, string? value)
 		{
 			var indirect = dlsym (handle, symbol);
 			if (indirect == IntPtr.Zero)
 				return;
-			Marshal.WriteIntPtr (indirect, value == null ? IntPtr.Zero : NSString.CreateNative (value));
+			Marshal.WriteIntPtr (indirect, CFString.CreateNative (value));
 		}
 
-		public static void SetString (IntPtr handle, string symbol, NSString value)
+		public static void SetString (IntPtr handle, string symbol, NSString? value)
 		{
 			var indirect = dlsym (handle, symbol);
 			if (indirect == IntPtr.Zero)
 				return;
-			var strHandle = value == null ? IntPtr.Zero : value.Handle;
+			var strHandle = value.GetHandle ();
 			if (strHandle != IntPtr.Zero)
 				CFObject.CFRetain (strHandle);
 			Marshal.WriteIntPtr (indirect, strHandle);
 		}
 
-		public static void SetArray (IntPtr handle, string symbol, NSArray array)
+		public static void SetArray (IntPtr handle, string symbol, NSArray? array)
 		{
 			var indirect = dlsym (handle, symbol);
 			if (indirect == IntPtr.Zero)
 				return;
-			var arrayHandle = array == null ? IntPtr.Zero : array.Handle;
+			var arrayHandle = array.GetHandle ();
 			if (arrayHandle != IntPtr.Zero)
 				CFObject.CFRetain (arrayHandle);
 			Marshal.WriteIntPtr (indirect, arrayHandle);
@@ -435,7 +438,7 @@ namespace ObjCRuntime {
 			}
 		}
 		
-		internal static int SlowGetInt32 (string lib, string symbol)
+		internal static int SlowGetInt32 (string? lib, string symbol)
 		{
 			var handle = dlopen (lib, 0);
 			if (handle == IntPtr.Zero)
@@ -447,7 +450,7 @@ namespace ObjCRuntime {
 			}
 		}
 
-		internal static long SlowGetInt64 (string lib, string symbol)
+		internal static long SlowGetInt64 (string? lib, string symbol)
 		{
 			var handle = dlopen (lib, 0);
 			if (handle == IntPtr.Zero)
@@ -459,7 +462,7 @@ namespace ObjCRuntime {
 			}
 		}
 
-		internal static IntPtr SlowGetIntPtr (string lib, string symbol)
+		internal static IntPtr SlowGetIntPtr (string? lib, string symbol)
 		{
 			var handle = dlopen (lib, 0);
 			if (handle == IntPtr.Zero)
@@ -471,7 +474,7 @@ namespace ObjCRuntime {
 			}
 		}
 
-		internal static double SlowGetDouble (string lib, string symbol)
+		internal static double SlowGetDouble (string? lib, string symbol)
 		{
 			var handle = dlopen (lib, 0);
 			if (handle == IntPtr.Zero)
@@ -483,7 +486,7 @@ namespace ObjCRuntime {
 			}
 		}
 
-		internal static NSString SlowGetStringConstant (string lib, string symbol)
+		internal static NSString? SlowGetStringConstant (string? lib, string symbol)
 		{
 			var handle = dlopen (lib, 0);
 			if (handle == IntPtr.Zero)
diff --git a/src/generator.cs b/src/generator.cs
index 03ac0a7232..af21582c69 100644
--- a/src/generator.cs
+++ b/src/generator.cs
@@ -6972,7 +6972,7 @@ public partial class Generator : IMemberGatherer {
 					if (field_pi.PropertyType == TypeManager.NSString){
 						print ("if (_{0} is null)", field_pi.Name);
 						indent++;
-						print ("_{0} = Dlfcn.GetStringConstant (Libraries.{2}.Handle, \"{1}\");", field_pi.Name, fieldAttr.SymbolName, library_name);
+						print ("_{0} = Dlfcn.GetStringConstant (Libraries.{2}.Handle, \"{1}\")!;", field_pi.Name, fieldAttr.SymbolName, library_name);
 						indent--;
 						print ("return _{0};", field_pi.Name);
 					} else if (field_pi.PropertyType.Name == "NSArray"){
@@ -7024,7 +7024,7 @@ public partial class Generator : IMemberGatherer {
 						if (smartEnumTypeName != null) {
 							print ("if (_{0} is null)", field_pi.Name);
 							indent++;
-							print ("_{0} = Dlfcn.GetStringConstant (Libraries.{2}.Handle, \"{1}\");", field_pi.Name, fieldAttr.SymbolName, library_name);
+							print ("_{0} = Dlfcn.GetStringConstant (Libraries.{2}.Handle, \"{1}\")!;", field_pi.Name, fieldAttr.SymbolName, library_name);
 							indent--;
 							print ($"return {smartEnumTypeName}Extensions.GetValue (_{field_pi.Name});");
 						} else if (GetNativeEnumToManagedExpression (field_pi.PropertyType, out var preExpression, out var postExpression, out var _)) {