diff --git a/src/eval.c b/src/eval.c
index c2856fe..923e7a4 100644
--- a/src/eval.c
+++ b/src/eval.c
@@ -2163,6 +2163,8 @@
 	    }
 	}
 	lp->ll_name = lp->ll_exp_name;
+	if (lp->ll_name != NULL)
+	    lp->ll_name_end = lp->ll_name + STRLEN(lp->ll_name);
     }
     else
     {
@@ -2373,7 +2375,7 @@
 
 	    // handle +=, -=, *=, /=, %= and .=
 	    di = NULL;
-	    if (eval_variable(lp->ll_name, (int)(lp->ll_name_end - lp->ll_name),
+	    if (eval_variable(lp->ll_name, (int)STRLEN(lp->ll_name),
 				 lp->ll_sid, &tv, &di, EVAL_VAR_VERBOSE) == OK)
 	    {
 		if (di != NULL && check_typval_is_value(&di->di_tv) == FAIL)