diff --git a/src/os_unix.c b/src/os_unix.c
index 43ac4ae..ba74a2d 100644
--- a/src/os_unix.c
+++ b/src/os_unix.c
@@ -143,7 +143,7 @@
 
 #ifdef FEAT_XCLIPBOARD
 static int do_xterm_trace __ARGS((void));
-#define XT_TRACE_DELAY	50	/* delay for xterm tracing */
+# define XT_TRACE_DELAY	50	/* delay for xterm tracing */
 #endif
 
 static void handle_resize __ARGS((void));