diff --git a/json.zig b/json.zig
index 3aaf89000306fb8feedd1b5750c7c1e135e31d63..19b7c58d8dca5abc868a0db0cf35f3f86e9cd600 100644
--- a/json.zig
+++ b/json.zig
@@ -353,7 +353,7 @@ const Parser = struct {
         return p.slice()[0..n].*;
     }
 
-    pub fn addObject(p: *Parser, alloc: std.mem.Allocator, members: *ObjectHashMap) !ValueIndex {
+    pub fn addObject(p: *Parser, alloc: std.mem.Allocator, members: *const ObjectHashMap) !ValueIndex {
         const t = tracer.trace(@src(), "({d})", .{members.entries.len});
         defer t.end();