diff --git a/common/boot_control_interface.h b/common/boot_control_interface.h
index 776333c..1b76939 100644
--- a/common/boot_control_interface.h
+++ b/common/boot_control_interface.h
@@ -33,7 +33,7 @@
 class BootControlInterface {
  public:
   using Slot = unsigned int;
-  using PartitionSizes = std::map<std::string, uint64_t>;
+  using PartitionMetadata = std::map<std::string, uint64_t>;
 
   static const Slot kInvalidSlot = UINT_MAX;
 
@@ -81,11 +81,11 @@
 
   // Initialize metadata of underlying partitions for a given |slot|.
   // Ensure that partitions at the specified |slot| has a given size, as
-  // specified by |partition_sizes|. |partition_sizes| has the format:
+  // specified by |partition_metadata|. |partition_metadata| has the format:
   // {"vendor": 524288000, "system": 2097152000, ...}; values must be
   // aligned to the logical block size of the super partition.
-  virtual bool InitPartitionMetadata(Slot slot,
-                                     const PartitionSizes& partition_sizes) = 0;
+  virtual bool InitPartitionMetadata(
+      Slot slot, const PartitionMetadata& partition_metadata) = 0;
 
   // Do necessary clean-up operations after the whole update.
   virtual void Cleanup() = 0;
diff --git a/common/boot_control_stub.cc b/common/boot_control_stub.cc
index 2e326e5..ca880d4 100644
--- a/common/boot_control_stub.cc
+++ b/common/boot_control_stub.cc
@@ -60,7 +60,7 @@
 }
 
 bool BootControlStub::InitPartitionMetadata(
-    Slot slot, const PartitionSizes& partition_sizes) {
+    Slot slot, const PartitionMetadata& partition_metadata) {
   LOG(ERROR) << __FUNCTION__ << " should never be called.";
   return false;
 }
diff --git a/common/boot_control_stub.h b/common/boot_control_stub.h
index 65248af..0950997 100644
--- a/common/boot_control_stub.h
+++ b/common/boot_control_stub.h
@@ -45,8 +45,8 @@
   bool MarkSlotUnbootable(BootControlInterface::Slot slot) override;
   bool SetActiveBootSlot(BootControlInterface::Slot slot) override;
   bool MarkBootSuccessfulAsync(base::Callback<void(bool)> callback) override;
-  bool InitPartitionMetadata(Slot slot,
-                             const PartitionSizes& partition_sizes) override;
+  bool InitPartitionMetadata(
+      Slot slot, const PartitionMetadata& partition_metadata) override;
   void Cleanup() override;
 
  private:
diff --git a/common/fake_boot_control.h b/common/fake_boot_control.h
index e71c83a..513c149 100644
--- a/common/fake_boot_control.h
+++ b/common/fake_boot_control.h
@@ -74,8 +74,8 @@
     return true;
   }
 
-  bool InitPartitionMetadata(Slot slot,
-                             const PartitionSizes& partition_sizes) override {
+  bool InitPartitionMetadata(
+      Slot slot, const PartitionMetadata& partition_metadata) override {
     return true;
   }