diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index c86b510..538d741 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -85,16 +85,16 @@ jobs:
           msys2 -c 'pacman --noconfirm -Suu'
       - name: debug build
         run: |
-          build_msys2.bat
-        shell: cmd
+          ./build_msys2.bat
+        shell: msys2 {0}
         env:
           CC: gcc
           CXX: g++
           PATH: D:\a\_temp\msys\msys64\usr\bin;D:\a\_temp\msys\msys64\${{ matrix.msystem_lower }}\bin;D:\a\_temp\msys
       - name: release build
         run: |
-          build_msys2.bat --release
-        shell: cmd
+          ./build_msys2.bat --release
+        shell: msys2 {0}
         env:
           CC: gcc
           CXX: g++
diff --git a/build_msys2.bat b/build_msys2.bat
index e1d53e1..fe38cde 100644
--- a/build_msys2.bat
+++ b/build_msys2.bat
@@ -28,6 +28,8 @@ if defined SOMETHING_RELEASE (
     config_indexer assets/vars.conf >src/config_index.hpp
     %CXX% %CXXFLAGS% %PKGSCFLAGS% -o something.debug.exe src/something.cpp %PKGLIBS% -lopengl32 -static
 )
+dir *.exe
+REM Returns Errorcode. Zero is Noerror.
+EXIT /B %ERRORLEVEL%
 endlocal
 
-dir *.exe
diff --git a/src/something_main.cpp b/src/something_main.cpp
index 8904d6a..214f579 100644
--- a/src/something_main.cpp
+++ b/src/something_main.cpp
@@ -6,13 +6,20 @@ const Seconds DELTA_TIME_SECS = 1.0f / static_cast<Seconds>(SCREEN_FPS);
 const Milliseconds DELTA_TIME_MS =
     static_cast<Milliseconds>(floorf(DELTA_TIME_SECS * 1000.0f));
 
-void MessageCallback(GLenum source,
-                     GLenum type,
-                     GLuint id,
-                     GLenum severity,
-                     GLsizei length,
-                     const GLchar* message,
-                     const void* userParam)
+// inspired by https://github.com/Velho/ded/commit/44f9223d6ea7278243fa56c5a0c095bba0db4450
+#if defined(__MINGW32__)  || defined(__MINGW64__)
+#define CALLING_METHOD __stdcall
+#else
+#define CALLING_METHOD 
+#endif
+
+void CALLING_METHOD MessageCallback(GLenum source,
+                                    GLenum type,
+                                    GLuint id,
+                                    GLenum severity,
+                                    GLsizei length,
+                                    const GLchar* message,
+                                    const void* userParam)
 {
     (void) source;
     (void) id;