diff --git a/src/vppinfra/format.h b/src/vppinfra/format.h
index a1a70a2..14bac86 100644
--- a/src/vppinfra/format.h
+++ b/src/vppinfra/format.h
@@ -372,6 +372,8 @@
 created circular dependency problems. */
 int test_vec_main (unformat_input_t * input);
 
+char *format_c_string (u8 *s, const char *fmt, ...);
+
 #endif /* included_format_h */
 
 /*