diff --git a/src/eval.c b/src/eval.c
index 72b1d6c..7bc37f2 100644
--- a/src/eval.c
+++ b/src/eval.c
@@ -291,7 +291,7 @@
     }
     else
     {
-	s = tv_get_string_buf_chk(expr, buf);
+	s = tv_get_string_buf_chk_strict(expr, buf, TRUE);
 	if (s == NULL)
 	    return FAIL;
 	s = skipwhite(s);