diff --git a/vlib/builtin/map.v b/vlib/builtin/map.v
index 85c9cced794e20..358441f1e88a6e 100644
--- a/vlib/builtin/map.v
+++ b/vlib/builtin/map.v
@@ -249,10 +249,20 @@ fn new_map_1(value_bytes int) map {
 }
 
 fn new_map_init(n int, value_bytes int, keys &string, values voidptr) map {
-	mut out := new_map_1(value_bytes)
+	return new_map_init_1<string>(n, value_bytes, keys, values)
+}
+
+fn new_map_init_1<T>(n int, value_bytes int, keys voidptr, values voidptr) map {
+	mut out := new_map<T>(value_bytes)
 	// TODO pre-allocate n slots
-	for i in 0 .. n {
-		unsafe {out.set(keys[i], byteptr(values) + i * value_bytes)}
+	mut pkey := byteptr(keys)
+	mut pval := byteptr(values)
+	for _ in 0 .. n {
+		unsafe {
+			out.set_1(pkey, pval)
+			pkey += out.key_bytes
+			pval += value_bytes
+		}
 	}
 	return out
 }