diff --git a/include/libbb.h b/include/libbb.h
index ead1020..fccc816 100644
--- a/include/libbb.h
+++ b/include/libbb.h
@@ -1277,6 +1277,7 @@
  * on first call.
  */
 int64_t read_key(int fd, char *buffer) FAST_FUNC;
+void read_key_ungets(char *buffer, const char *str, unsigned len) FAST_FUNC;
 
 
 #if ENABLE_FEATURE_EDITING