diff --git a/src/OutputAPI.hxx b/src/OutputAPI.hxx
index 73cbaf183..e905fd9db 100644
--- a/src/OutputAPI.hxx
+++ b/src/OutputAPI.hxx
@@ -18,7 +18,7 @@
  */
 
 #ifndef MPD_OUTPUT_API_HXX
-#define MPD_OUTPUT_API_HxX
+#define MPD_OUTPUT_API_HXX
 
 #include "OutputPlugin.hxx"
 #include "OutputInternal.hxx"