diff --git a/src/OutputAPI.hxx b/src/OutputAPI.hxx
index b101b9429..322ed3971 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
 
 // IWYU pragma: begin_exports