diff --git a/gl/lib/targetdir.h b/gl/lib/targetdir.h
index cb6b06835..558853e4d 100644
--- a/gl/lib/targetdir.h
+++ b/gl/lib/targetdir.h
@@ -20,7 +20,7 @@
 #include <sys/stat.h>
 
 #ifndef _GL_INLINE_HEADER_BEGIN
- #error "Please include config.h first."
+# error "Please include config.h first."
 #endif
 _GL_INLINE_HEADER_BEGIN
 #ifndef TARGETDIR_INLINE