diff --git a/vlib/builtin/string.v b/vlib/builtin/string.v
index 515b202133..8b2981b181 100644
--- a/vlib/builtin/string.v
+++ b/vlib/builtin/string.v
@@ -604,9 +604,17 @@ fn (s string) substr2(start int, _end int, end_max bool) string {
 // Example: assert 'ABCD'.substr(1,3) == 'BC'
 pub fn (s string) substr(start int, end int) string {
 	$if !no_bounds_checking ? {
-		if start > end || start > s.len || end > s.len || start < 0 || end < 0 {
-			panic('substr($start, $end) out of bounds (len=$s.len)')
+		/*
+		$if debug {
+			if start > end || start > s.len || end > s.len || start < 0 || end < 0 {
+				println('substr($start, $end) out of bounds (len=$s.len)')
+				println('s="$s"')
+				print_backtrace()
+				return ''
+			}
 		}
+		*/
+		panic('substr($start, $end) out of bounds (len=$s.len)')
 	}
 	len := end - start
 	if len == s.len {
diff --git a/vlib/net/urllib/urllib.v b/vlib/net/urllib/urllib.v
index 72ca25cf11..17e354a9e7 100644
--- a/vlib/net/urllib/urllib.v
+++ b/vlib/net/urllib/urllib.v
@@ -745,8 +745,12 @@ pub fn (u URL) str() string {
 			// preceded by a dot-segment (e.g., './this:that') to make a relative-
 			// path reference.
 			i := path.index_byte(`:`)
-			if i > -1 && path[..i].index_byte(`/`) == -1 {
-				buf.write_string('./')
+			if i > -1 {
+				// TODO remove this when autofree handles tmp
+				// expressions like this
+				if i > -1 && path[..i].index_byte(`/`) == -1 {
+					buf.write_string('./')
+				}
 			}
 		}
 		buf.write_string(path)