diff --git a/include/string.h b/include/string.h
index ef331bd9d8d..2b725a7e59d 100644
--- a/include/string.h
+++ b/include/string.h
@@ -74,6 +74,7 @@ FAR char  *strncpy(FAR char *, FAR const char *, size_t);
 FAR char  *stpncpy(FAR char *, FAR const char *, size_t);
 FAR char  *strpbrk(FAR const char *, FAR const char *);
 FAR char  *strchr(FAR const char *s, int c);
+FAR char  *strchrnul(FAR const char *s, int c);
 FAR char  *strrchr(FAR const char *s, int c);
 size_t     strspn(FAR const char *, FAR const char *);
 size_t     strcspn(FAR const char *, FAR const char *);
diff --git a/libs/libc/string/lib_strchrnul.c b/libs/libc/string/lib_strchrnul.c
index 851fcbf20d2..ab15fb96004 100644
--- a/libs/libc/string/lib_strchrnul.c
+++ b/libs/libc/string/lib_strchrnul.c
@@ -54,5 +54,5 @@ FAR char *strchrnul(FAR const char *s, int c)
         }
     }
 
-  return s;
+  return (FAR char *)s;
 }