diff --git a/src/compiler.ts b/src/compiler.ts
index 3dfdcabd6e..6955383478 100644
--- a/src/compiler.ts
+++ b/src/compiler.ts
@@ -6610,8 +6610,8 @@ export class Compiler extends DiagnosticEmitter {
         let overrideInstance = overrideInstances[i];
         if (!overrideInstance.is(CommonFlags.Compiled)) continue; // errored
 
-        const overrideSignature = overrideInstance.signature;
-        const originalSignature = instance.signature;
+        let overrideSignature = overrideInstance.signature;
+        let originalSignature = instance.signature;
 
         if (!overrideSignature.isAssignableTo(originalSignature, true)) {
           this.error(
diff --git a/src/types.ts b/src/types.ts
index fdaa22f278..30e6e42558 100644
--- a/src/types.ts
+++ b/src/types.ts
@@ -1053,11 +1053,10 @@ export class Signature {
     let targetThisType = target.thisType;
 
     if (thisThisType != null && targetThisType != null){
-      const compatibleThisType = checkCompatibleOverride ? thisThisType.canExtendOrImplement(targetThisType)
+      const compatibleThisType = checkCompatibleOverride 
+        ? thisThisType.canExtendOrImplement(targetThisType)
         : targetThisType.isAssignableTo(thisThisType);
-      if (!compatibleThisType) {
-        return false;
-      }
+      if (!compatibleThisType) return false; 
     }else if (thisThisType || targetThisType){
       return false;
     }
diff --git a/tests/compiler/class-member-function-as-parameter.ts b/tests/compiler/class-member-function-as-parameter.ts
index ec5b591a64..611f0fbf03 100644
--- a/tests/compiler/class-member-function-as-parameter.ts
+++ b/tests/compiler/class-member-function-as-parameter.ts
@@ -1,14 +1,19 @@
 class A {
   foo(): void { }
 }
+
 class B extends A {
   foo(): void { }
 }
+
 function foo(): void { }
+
 function consumeA(callback: (this: A) => void): void { }
 function consumeB(callback: (this: B) => void): void { }
+
 const a = new A();
 const b = new B();
+
 consumeB(a.foo); // shouldn't error
 consumeA(foo);   // should error
 consumeA(b.foo); // should error