diff --git a/vm_eval.c b/vm_eval.c
index edfcc6e435..7c7f5c0bf4 100644
--- a/vm_eval.c
+++ b/vm_eval.c
@@ -1709,7 +1709,7 @@ pm_eval_make_iseq(VALUE src, VALUE fname, int line,
                     continue;
                 }
 
-                pm_string_constant_init(scope_local, name, strlen(name));
+                pm_string_constant_init(scope_local, name, length);
             }
         }