diff --git a/libmpcodecs/img_format.c b/libmpcodecs/img_format.c
index 3b81c1f67e..f2e4bca51a 100644
--- a/libmpcodecs/img_format.c
+++ b/libmpcodecs/img_format.c
@@ -1,8 +1,10 @@
 #include "config.h"
 #include "img_format.h"
+#include "stdio.h"
 
 const char *vo_format_name(int format)
 {
+    static char unknow_format[20];
     switch(format)
     {
 	case IMGFMT_RGB1: return("RGB 1-bit");
@@ -66,5 +68,6 @@ const char *vo_format_name(int format)
 	case IMGFMT_XVMC_MOCO_MPEG2: return("MPEG1/2 Motion Compensation");
 	case IMGFMT_XVMC_IDCT_MPEG2: return("MPEG1/2 Motion Compensation and IDCT");
     }
-    return("Unknown");
+    snprintf(unknow_format,20,"Unknown 0x%04x",format);
+    return unknow_format;
 }