diff --git a/payload_consumer/payload_constants.cc b/payload_consumer/payload_constants.cc
index e47b4f8..3d78e0a 100644
--- a/payload_consumer/payload_constants.cc
+++ b/payload_consumer/payload_constants.cc
@@ -25,6 +25,7 @@
 const uint32_t kInPlaceMinorPayloadVersion = 1;
 const uint32_t kSourceMinorPayloadVersion = 2;
 const uint32_t kOpSrcHashMinorPayloadVersion = 3;
+const uint32_t kImgdiffMinorPayloadVersion = 4;
 
 const char kLegacyPartitionNameKernel[] = "boot";
 const char kLegacyPartitionNameRoot[] = "system";
diff --git a/payload_consumer/payload_constants.h b/payload_consumer/payload_constants.h
index c3cd363..76d740f 100644
--- a/payload_consumer/payload_constants.h
+++ b/payload_consumer/payload_constants.h
@@ -43,6 +43,9 @@
 // The minor version that allows per-operation source hash.
 extern const uint32_t kOpSrcHashMinorPayloadVersion;
 
+// The minor version that allows IMGDIFF operation.
+extern const uint32_t kImgdiffMinorPayloadVersion;
+
 
 // The kernel and rootfs partition names used by the BootControlInterface when
 // handling update payloads with a major version 1. The names of the updated