diff --git a/libasn1fix/asn1fix_internal.h b/libasn1fix/asn1fix_internal.h
index d4a5e84..9ca2904 100644
--- a/libasn1fix/asn1fix_internal.h
+++ b/libasn1fix/asn1fix_internal.h
@@ -104,8 +104,9 @@
 		int _save_errno = errno;			\
 		if(code < 0) {					\
 			if(arg->debug)				\
-			arg->debug(code, fmt " in %s (%s:%d)",	\
-				##args,				\
+				arg->debug(code,		\
+				"%s: " fmt " in %s (%s:%d)",	\
+				__func__, ##args,		\
 				arg->mod->source_file_name,	\
 				__FILE__, __LINE__);		\
 		} else if(arg->eh) {				\