diff --git a/js/public/RootingAPI.h b/js/public/RootingAPI.h
index 33f98d8dfba6..5b612660cd70 100644
--- a/js/public/RootingAPI.h
+++ b/js/public/RootingAPI.h
@@ -7,6 +7,7 @@
 #ifndef js_RootingAPI_h
 #define js_RootingAPI_h
 
+#include "mozilla/Attributes.h"
 #include "mozilla/GuardObjects.h"
 #include "mozilla/LinkedList.h"
 #include "mozilla/NullPtr.h"
@@ -437,10 +438,9 @@ class MOZ_NONHEAP_CLASS Handle : public js::HandleBase<T>
      *     for the lifetime of the handle, as its users may not expect its value
      *     to change underneath them.
      */
-    static Handle fromMarkedLocation(const T *p) {
-        Handle h;
-        h.ptr = p;
-        return h;
+    static MOZ_CONSTEXPR Handle fromMarkedLocation(const T *p) {
+        return Handle(p, DeliberatelyChoosingThisOverload,
+                      ImUsingThisOnlyInFromFromMarkedLocation);
     }
 
     /*
@@ -482,6 +482,10 @@ class MOZ_NONHEAP_CLASS Handle : public js::HandleBase<T>
   private:
     Handle() {}
 
+    enum Disambiguator { DeliberatelyChoosingThisOverload = 42 };
+    enum CallerIdentity { ImUsingThisOnlyInFromFromMarkedLocation = 17 };
+    MOZ_CONSTEXPR Handle(const T *p, Disambiguator, CallerIdentity) : ptr(p) {}
+
     const T *ptr;
 
     template <typename S> void operator=(S) MOZ_DELETE;
diff --git a/js/src/jit/Ion.h b/js/src/jit/Ion.h
index cb68dc7db088..88d8e8acb3ca 100644
--- a/js/src/jit/Ion.h
+++ b/js/src/jit/Ion.h
@@ -216,7 +216,7 @@ struct IonOptions
         baselineUsesBeforeCompile = 0;
     }
 
-    IonOptions()
+    MOZ_CONSTEXPR IonOptions()
       : gvn(true),
         gvnIsOptimistic(true),
         licm(true),
diff --git a/js/src/vm/ObjectImpl.h b/js/src/vm/ObjectImpl.h
index d2cc6b655e0e..d367507deae8 100644
--- a/js/src/vm/ObjectImpl.h
+++ b/js/src/vm/ObjectImpl.h
@@ -8,6 +8,7 @@
 #define vm_ObjectImpl_h
 
 #include "mozilla/Assertions.h"
+#include "mozilla/Attributes.h"
 
 #include <stdint.h>
 
@@ -833,7 +834,7 @@ class ObjectElements
     }
 
   public:
-    ObjectElements(uint32_t capacity, uint32_t length)
+    MOZ_CONSTEXPR ObjectElements(uint32_t capacity, uint32_t length)
       : flags(0), initializedLength(0), capacity(capacity), length(length)
     {}