diff --git a/csharp/ql/src/semmle/code/csharp/commons/Assertions.qll b/csharp/ql/src/semmle/code/csharp/commons/Assertions.qll
index 7ffea36fe44..5fa5bb92ad7 100644
--- a/csharp/ql/src/semmle/code/csharp/commons/Assertions.qll
+++ b/csharp/ql/src/semmle/code/csharp/commons/Assertions.qll
@@ -55,7 +55,8 @@ class Assertion extends MethodCall {
       bb = this.getAControlFlowNode().getBasicBlock() |
       result = bb.getASuccessor*()
     ) and
-    result.getASuccessor() = jb
+    result.getASuccessor() = jb and
+    not jb.dominates(result)
   }
 
   pragma[nomagic]
@@ -64,6 +65,8 @@ class Assertion extends MethodCall {
     forall(BasicBlock pred |
       pred = jb.getAPredecessor() |
       pred = this.getAPossiblyDominatedPredecessor(jb)
+      or
+      jb.dominates(pred)
     )
   }
 
diff --git a/csharp/ql/src/semmle/code/csharp/controlflow/ControlFlowElement.qll b/csharp/ql/src/semmle/code/csharp/controlflow/ControlFlowElement.qll
index f841c42d6a4..fcd0f61aa05 100644
--- a/csharp/ql/src/semmle/code/csharp/controlflow/ControlFlowElement.qll
+++ b/csharp/ql/src/semmle/code/csharp/controlflow/ControlFlowElement.qll
@@ -106,7 +106,8 @@ class ControlFlowElement extends ExprOrStmtParent, @control_flow_element {
       this.immediatelyControls(mid, s) |
       result = mid.getASuccessor*()
     ) and
-    result.getASuccessor() = controlled
+    result.getASuccessor() = controlled and
+    not controlled.dominates(result)
   }
 
   pragma[nomagic]
@@ -115,6 +116,8 @@ class ControlFlowElement extends ExprOrStmtParent, @control_flow_element {
     forall(BasicBlock pred |
       pred = controlled.getAPredecessor() |
       pred = this.getAPossiblyControlledPredecessor(controlled, s)
+      or
+      controlled.dominates(pred)
     )
   }
 
diff --git a/csharp/ql/test/library-tests/controlflow/guards/BooleanGuardedExpr.expected b/csharp/ql/test/library-tests/controlflow/guards/BooleanGuardedExpr.expected
index c440d85661c..194e3ab809f 100644
--- a/csharp/ql/test/library-tests/controlflow/guards/BooleanGuardedExpr.expected
+++ b/csharp/ql/test/library-tests/controlflow/guards/BooleanGuardedExpr.expected
@@ -62,6 +62,8 @@
 | Guards.cs:194:31:194:31 | access to parameter s | Guards.cs:193:14:193:25 | call to method NullTest3 | Guards.cs:193:24:193:24 | access to parameter s | false |
 | Guards.cs:196:31:196:31 | access to parameter s | Guards.cs:195:13:195:27 | call to method NotNullTest4 | Guards.cs:195:26:195:26 | access to parameter s | true |
 | Guards.cs:198:31:198:31 | access to parameter s | Guards.cs:197:14:197:29 | call to method NullTestWrong | Guards.cs:197:28:197:28 | access to parameter s | false |
+| Guards.cs:205:13:205:13 | access to parameter o | Guards.cs:203:13:203:21 | ... != ... | Guards.cs:203:13:203:13 | access to parameter o | true |
+| Guards.cs:208:17:208:17 | access to parameter o | Guards.cs:203:13:203:21 | ... != ... | Guards.cs:203:13:203:13 | access to parameter o | true |
 | Splitting.cs:13:17:13:17 | access to parameter o | Splitting.cs:12:17:12:25 | ... != ... | Splitting.cs:12:17:12:17 | access to parameter o | true |
 | Splitting.cs:23:24:23:24 | access to parameter o | Splitting.cs:22:17:22:25 | ... != ... | Splitting.cs:22:17:22:17 | access to parameter o | true |
 | Splitting.cs:25:13:25:13 | access to parameter o | Splitting.cs:22:17:22:25 | ... != ... | Splitting.cs:22:17:22:17 | access to parameter o | false |
diff --git a/csharp/ql/test/library-tests/controlflow/guards/GuardedExpr.expected b/csharp/ql/test/library-tests/controlflow/guards/GuardedExpr.expected
index c6ad430a3e4..a5ee326de52 100644
--- a/csharp/ql/test/library-tests/controlflow/guards/GuardedExpr.expected
+++ b/csharp/ql/test/library-tests/controlflow/guards/GuardedExpr.expected
@@ -155,6 +155,10 @@
 | Guards.cs:196:31:196:31 | access to parameter s | Guards.cs:195:13:195:27 | call to method NotNullTest4 | Guards.cs:195:26:195:26 | access to parameter s | true |
 | Guards.cs:196:31:196:31 | access to parameter s | Guards.cs:195:26:195:26 | access to parameter s | Guards.cs:195:26:195:26 | access to parameter s | non-null |
 | Guards.cs:198:31:198:31 | access to parameter s | Guards.cs:197:14:197:29 | call to method NullTestWrong | Guards.cs:197:28:197:28 | access to parameter s | false |
+| Guards.cs:205:13:205:13 | access to parameter o | Guards.cs:203:13:203:13 | access to parameter o | Guards.cs:203:13:203:13 | access to parameter o | non-null |
+| Guards.cs:205:13:205:13 | access to parameter o | Guards.cs:203:13:203:21 | ... != ... | Guards.cs:203:13:203:13 | access to parameter o | true |
+| Guards.cs:208:17:208:17 | access to parameter o | Guards.cs:203:13:203:13 | access to parameter o | Guards.cs:203:13:203:13 | access to parameter o | non-null |
+| Guards.cs:208:17:208:17 | access to parameter o | Guards.cs:203:13:203:21 | ... != ... | Guards.cs:203:13:203:13 | access to parameter o | true |
 | Splitting.cs:13:17:13:17 | access to parameter o | Splitting.cs:12:17:12:17 | access to parameter o | Splitting.cs:12:17:12:17 | access to parameter o | non-null |
 | Splitting.cs:13:17:13:17 | access to parameter o | Splitting.cs:12:17:12:25 | ... != ... | Splitting.cs:12:17:12:17 | access to parameter o | true |
 | Splitting.cs:23:24:23:24 | access to parameter o | Splitting.cs:22:17:22:17 | access to parameter o | Splitting.cs:22:17:22:17 | access to parameter o | non-null |
diff --git a/csharp/ql/test/library-tests/controlflow/guards/Guards.cs b/csharp/ql/test/library-tests/controlflow/guards/Guards.cs
index 2c0753a8133..8eeff60e992 100644
--- a/csharp/ql/test/library-tests/controlflow/guards/Guards.cs
+++ b/csharp/ql/test/library-tests/controlflow/guards/Guards.cs
@@ -197,4 +197,16 @@ public class Guards
         if (!NullTestWrong(s))
             Console.WriteLine(s); // not null guarded
     }
+
+    void M17(object o, string[] args)
+    {
+        if (o != null)
+        {
+            o.ToString(); // null guarded
+            foreach (var arg in args)
+            {
+                o.ToString(); // null guarded
+            }
+        }
+    }
 }
diff --git a/csharp/ql/test/library-tests/controlflow/guards/Implications.expected b/csharp/ql/test/library-tests/controlflow/guards/Implications.expected
index de01947a7f4..1cf80d3f0b0 100644
--- a/csharp/ql/test/library-tests/controlflow/guards/Implications.expected
+++ b/csharp/ql/test/library-tests/controlflow/guards/Implications.expected
@@ -200,6 +200,8 @@
 | Guards.cs:195:13:195:27 | call to method NotNullTest4 | true | Guards.cs:195:26:195:26 | access to parameter s | non-null |
 | Guards.cs:197:13:197:29 | !... | false | Guards.cs:197:14:197:29 | call to method NullTestWrong | true |
 | Guards.cs:197:13:197:29 | !... | true | Guards.cs:197:14:197:29 | call to method NullTestWrong | false |
+| Guards.cs:203:13:203:21 | ... != ... | false | Guards.cs:203:13:203:13 | access to parameter o | null |
+| Guards.cs:203:13:203:21 | ... != ... | true | Guards.cs:203:13:203:13 | access to parameter o | non-null |
 | Splitting.cs:12:17:12:25 | ... != ... | false | Splitting.cs:12:17:12:17 | access to parameter o | null |
 | Splitting.cs:12:17:12:25 | ... != ... | true | Splitting.cs:12:17:12:17 | access to parameter o | non-null |
 | Splitting.cs:22:17:22:25 | ... != ... | false | Splitting.cs:22:17:22:17 | access to parameter o | null |
diff --git a/csharp/ql/test/library-tests/controlflow/guards/NullGuardedExpr.expected b/csharp/ql/test/library-tests/controlflow/guards/NullGuardedExpr.expected
index 863b122aba8..6b7be8f1f51 100644
--- a/csharp/ql/test/library-tests/controlflow/guards/NullGuardedExpr.expected
+++ b/csharp/ql/test/library-tests/controlflow/guards/NullGuardedExpr.expected
@@ -39,6 +39,8 @@
 | Guards.cs:192:31:192:31 | access to parameter s |
 | Guards.cs:194:31:194:31 | access to parameter s |
 | Guards.cs:196:31:196:31 | access to parameter s |
+| Guards.cs:205:13:205:13 | access to parameter o |
+| Guards.cs:208:17:208:17 | access to parameter o |
 | Splitting.cs:13:17:13:17 | access to parameter o |
 | Splitting.cs:23:24:23:24 | access to parameter o |
 | Splitting.cs:35:13:35:13 | access to parameter o |