diff --git a/src/gl/inject_glx.cpp b/src/gl/inject_glx.cpp
index 54e97bb..34a3599 100644
--- a/src/gl/inject_glx.cpp
+++ b/src/gl/inject_glx.cpp
@@ -170,7 +170,7 @@ EXPORT_C_(int64_t) glXSwapBuffersMscOML(void* dpy, void* drawable, int64_t targe
 {
     glx.Load();
     if (!glx.SwapBuffersMscOML)
-        return 0;
+        return -1;
 
     do_imgui_swap(dpy, drawable);
     int64_t ret = glx.SwapBuffersMscOML(dpy, drawable, target_msc, divisor, remainder);