diff --git a/gtk/fallback-c89.c b/gtk/fallback-c89.c
index df28048feb..0202677c71 100644
--- a/gtk/fallback-c89.c
+++ b/gtk/fallback-c89.c
@@ -18,7 +18,8 @@
  */
 
 #include <math.h>
- 
+#include "config.h"
+
 /* Workaround for round() for non-GCC/non-C99 compilers */
 #ifndef HAVE_ROUND
 static inline double