diff --git a/json.zig b/json.zig
index e1a09219174e3abb0fc801e0742a639d40473234..7d426e1e21b0bfc643554fd2ce67bea95c88a2a4 100644
--- a/json.zig
+++ b/json.zig
@@ -138,6 +138,7 @@ fn parseString(alloc: std.mem.Allocator, p: *Parser) anyerror!?StringIndex {
             break;
         }
         if (c != '\\') {
+            if (c < 0x20) return error.JsonExpectedTODO;
             const l = std.unicode.utf8CodepointSequenceLength(c) catch unreachable;
             const b = p.temp.items[p.idx - l ..][0..l];
             try characters.appendSlice(b);