diff --git a/object/types.proto b/object/types.proto
index 8169645..302019f 100644
--- a/object/types.proto
+++ b/object/types.proto
@@ -41,6 +41,9 @@ enum MatchType {
 
   // Lack of key
   NOT_PRESENT = 3;
+
+  // String prefix match
+  COMMON_PREFIX = 4;
 }
 
 // Short header fields