diff --git a/lib/rb/ext/compact_protocol.c b/lib/rb/ext/compact_protocol.c
index 33a1f9f..768b2e5 100644
--- a/lib/rb/ext/compact_protocol.c
+++ b/lib/rb/ext/compact_protocol.c
@@ -458,6 +458,7 @@
     
     if (modifier == 0) {
       // not a delta. look ahead for the zigzag varint field id.
+      LAST_ID(self);
       field_id = read_i16(self);
     } else {
       // has a delta. add the delta to the last read field id.