diff --git a/Tests/SwiftMix/CMain.c b/Tests/SwiftMix/CMain.c
index 8877da4301..519058efe1 100644
--- a/Tests/SwiftMix/CMain.c
+++ b/Tests/SwiftMix/CMain.c
@@ -1,5 +1,5 @@
-extern int ObjCMain(int argc, char const* const argv[]);
-int main(int argc, char* argv[])
+extern int ObjCMain(void);
+int main(void)
 {
-  return ObjCMain(argc, argv);
+  return ObjCMain();
 }
diff --git a/Tests/SwiftMix/CMakeLists.txt b/Tests/SwiftMix/CMakeLists.txt
index 5e50470f66..6d8e48bd06 100644
--- a/Tests/SwiftMix/CMakeLists.txt
+++ b/Tests/SwiftMix/CMakeLists.txt
@@ -3,3 +3,4 @@ project(SwiftMix C Swift)
 
 add_executable(SwiftMix CMain.c ObjCMain.m SwiftMain.swift ObjC-Swift.h)
 set_property(TARGET SwiftMix PROPERTY XCODE_ATTRIBUTE_SWIFT_OBJC_BRIDGING_HEADER "ObjC-Swift.h")
+target_compile_options(SwiftMix PRIVATE "$<$<COMPILE_LANGUAGE:C>:-Werror=objc-method-access>")
diff --git a/Tests/SwiftMix/ObjCMain.m b/Tests/SwiftMix/ObjCMain.m
index 20f0bf1eec..afc924380c 100644
--- a/Tests/SwiftMix/ObjCMain.m
+++ b/Tests/SwiftMix/ObjCMain.m
@@ -1,4 +1,4 @@
 #import "SwiftMix-Swift.h"
-int ObjCMain(int argc, char const* const argv[]) {
+int ObjCMain(void) {
   return [SwiftMainClass SwiftMain];
 }
diff --git a/Tests/SwiftMix/SwiftMain.swift b/Tests/SwiftMix/SwiftMain.swift
index a4a0a62b43..d9c8cd7564 100644
--- a/Tests/SwiftMix/SwiftMain.swift
+++ b/Tests/SwiftMix/SwiftMain.swift
@@ -1,7 +1,7 @@
 import Foundation
 
 @objc class SwiftMainClass : NSObject {
-  class func SwiftMain() -> Int32 {
+  @objc class func SwiftMain() -> Int32 {
     dump("Hello World!");
     return 0;
   }