diff --git a/core/libc/libc.factor b/core/libc/libc.factor
index 756d29e551..70850a2894 100755
--- a/core/libc/libc.factor
+++ b/core/libc/libc.factor
@@ -73,3 +73,6 @@ PRIVATE>
 
 : with-malloc ( size quot -- )
     swap 1 calloc [ swap keep ] [ free ] [ ] cleanup ; inline
+
+: strlen ( alien -- len )
+    "size_t" "libc" "strlen" { "char*" } alien-invoke ;