diff --git a/src/if_ruby.c b/src/if_ruby.c
index 80ffa49..90e814e 100644
--- a/src/if_ruby.c
+++ b/src/if_ruby.c
@@ -733,7 +733,7 @@
 	vim_free(sval);
 	if (enc)
 	{
-	    return rb_enc_str_new(s, strlen(s), enc);
+	    return rb_enc_str_new(s, (long)strlen(s), enc);
 	}
     }
 #endif