diff --git a/waveflag.c b/waveflag.c
index 7d80241a0..605b9b1a7 100644
--- a/waveflag.c
+++ b/waveflag.c
@@ -17,6 +17,7 @@
  */
 
 #include <cairo.h>
+#include <libgen.h> // basename
 #include <math.h>
 #include <stdint.h>
 #include <stdio.h>