diff --git a/src/libraries/System.Reflection.Emit/tests/MethodBuilder/MethodBuilderSetReturnType.cs b/src/libraries/System.Reflection.Emit/tests/MethodBuilder/MethodBuilderSetReturnType.cs
index 6245fbb2dccf26..7fe59ee9b09da2 100644
--- a/src/libraries/System.Reflection.Emit/tests/MethodBuilder/MethodBuilderSetReturnType.cs
+++ b/src/libraries/System.Reflection.Emit/tests/MethodBuilder/MethodBuilderSetReturnType.cs
@@ -132,7 +132,6 @@ public void SetReturnType_TypeCreated_Works()
         }
 
         [Fact]
-        [ActiveIssue("https://github.com/dotnet/runtime/issues/2389", TestRuntimes.Mono)]
         public void SetReturnType_NullReturnType_ReturnsVoid()
         {
             TypeBuilder type = Helpers.DynamicType(TypeAttributes.Abstract);
diff --git a/src/mono/System.Private.CoreLib/src/System/Reflection/Emit/RuntimeMethodBuilder.Mono.cs b/src/mono/System.Private.CoreLib/src/System/Reflection/Emit/RuntimeMethodBuilder.Mono.cs
index 8e4503ce9934f9..4083d7378ac1a8 100644
--- a/src/mono/System.Private.CoreLib/src/System/Reflection/Emit/RuntimeMethodBuilder.Mono.cs
+++ b/src/mono/System.Private.CoreLib/src/System/Reflection/Emit/RuntimeMethodBuilder.Mono.cs
@@ -603,7 +603,9 @@ protected override void SetSignatureCore(Type? returnType, Type[]? returnTypeReq
                 Array.Copy(parameterTypes, this.parameters, parameterTypes.Length);
             }
 
-            rtype = returnType;
+            if (returnType != null)
+                rtype = returnType;
+
             returnModReq = returnTypeRequiredCustomModifiers;
             returnModOpt = returnTypeOptionalCustomModifiers;
             paramModReq = parameterTypeRequiredCustomModifiers;