diff --git a/core/encoding/json/marshal.odin b/core/encoding/json/marshal.odin
index 8cc814fcf..8f7749aba 100644
--- a/core/encoding/json/marshal.odin
+++ b/core/encoding/json/marshal.odin
@@ -85,6 +85,7 @@ marshal_to_writer :: proc(w: io.Writer, v: any, opt: ^Marshal_Options) -> (err:
 		case i16:     u = u128(i)
 		case i32:     u = u128(i)
 		case i64:     u = u128(i)
+		case i128:    u = u128(i)
 		case int:     u = u128(i)
 		case u8:      u = u128(i)
 		case u16:     u = u128(i)