diff --git a/common/dynamic_partition_control_interface.h b/common/dynamic_partition_control_interface.h
index 7289dee..7c2d0b0 100644
--- a/common/dynamic_partition_control_interface.h
+++ b/common/dynamic_partition_control_interface.h
@@ -130,6 +130,13 @@
   // the result in |path|. Returns true on success.
   // Sample result: /dev/block/by-name/
   virtual bool GetDeviceDir(std::string* path) = 0;
+
+  // Verifies that the untouched dynamic partitions in the target metadata have
+  // the same extents as the source metadata.
+  virtual bool VerifyExtentsForUntouchedPartitions(
+      uint32_t source_slot,
+      uint32_t target_slot,
+      const std::vector<std::string>& partitions) = 0;
 };
 
 }  // namespace chromeos_update_engine
diff --git a/common/dynamic_partition_control_stub.cc b/common/dynamic_partition_control_stub.cc
index cde36af..5a8ca43 100644
--- a/common/dynamic_partition_control_stub.cc
+++ b/common/dynamic_partition_control_stub.cc
@@ -76,4 +76,11 @@
   return true;
 }
 
+bool DynamicPartitionControlStub::VerifyExtentsForUntouchedPartitions(
+    uint32_t source_slot,
+    uint32_t target_slot,
+    const std::vector<std::string>& partitions) {
+  return true;
+}
+
 }  // namespace chromeos_update_engine
diff --git a/common/dynamic_partition_control_stub.h b/common/dynamic_partition_control_stub.h
index 28e3e6a..94dba1b 100644
--- a/common/dynamic_partition_control_stub.h
+++ b/common/dynamic_partition_control_stub.h
@@ -51,6 +51,11 @@
   bool ListDynamicPartitionsForSlot(
       uint32_t current_slot, std::vector<std::string>* partitions) override;
   bool GetDeviceDir(std::string* path) override;
+
+  bool VerifyExtentsForUntouchedPartitions(
+      uint32_t source_slot,
+      uint32_t target_slot,
+      const std::vector<std::string>& partitions) override;
 };
 
 }  // namespace chromeos_update_engine