diff --git a/src/compiler/checker.ts b/src/compiler/checker.ts
index 43c9818e623..fa65b82f41b 100644
--- a/src/compiler/checker.ts
+++ b/src/compiler/checker.ts
@@ -16183,6 +16183,11 @@ namespace ts {
                 isTypeAny(getReturnTypeOfSignature(s));
         }
 
+        function isStrictSignature(sig: Signature) {
+            const kind = sig.declaration ? sig.declaration.kind : SyntaxKind.Unknown;
+            return kind !== SyntaxKind.MethodDeclaration && kind !== SyntaxKind.MethodSignature && kind !== SyntaxKind.Constructor;
+        }
+
         /**
          * See signatureRelatedTo, compareSignaturesIdentical
          */
@@ -16226,9 +16231,7 @@ namespace ts {
                 return Ternary.False;
             }
 
-            const kind = target.declaration ? target.declaration.kind : SyntaxKind.Unknown;
-            const strictVariance = !(checkMode & SignatureCheckMode.Callback) && strictFunctionTypes && kind !== SyntaxKind.MethodDeclaration &&
-                kind !== SyntaxKind.MethodSignature && kind !== SyntaxKind.Constructor;
+            const strictVariance = !(checkMode & SignatureCheckMode.Callback) && strictFunctionTypes && (isStrictSignature(target) || isStrictSignature(source));
             let result = Ternary.True;
 
             const sourceThisType = getThisTypeOfSignature(source);