diff --git a/src/assembler.h b/src/assembler.h
index 0779b58..3096266 100644
--- a/src/assembler.h
+++ b/src/assembler.h
@@ -359,8 +359,7 @@
   virtual void CopyRef(FrameOffset dest, FrameOffset src,
                        ManagedRegister scratch) = 0;
 
-  virtual void Copy(FrameOffset dest, FrameOffset src, ManagedRegister scratch,
-                    unsigned int size) = 0;
+  virtual void Copy(FrameOffset dest, FrameOffset src, ManagedRegister scratch, size_t size) = 0;
 
   virtual void Copy(FrameOffset dest, ManagedRegister src_base, Offset src_offset,
                     ManagedRegister scratch, size_t size) = 0;
diff --git a/src/assembler_arm.h b/src/assembler_arm.h
index f6be2b9..2a721ea 100644
--- a/src/assembler_arm.h
+++ b/src/assembler_arm.h
@@ -481,8 +481,7 @@
   virtual void CopyRef(FrameOffset dest, FrameOffset src,
                        ManagedRegister scratch);
 
-  virtual void Copy(FrameOffset dest, FrameOffset src, ManagedRegister scratch,
-                    unsigned int size);
+  virtual void Copy(FrameOffset dest, FrameOffset src, ManagedRegister scratch, size_t size);
 
   virtual void Copy(FrameOffset dest, ManagedRegister src_base, Offset src_offset,
                     ManagedRegister scratch, size_t size);
diff --git a/src/assembler_x86.h b/src/assembler_x86.h
index 6781e70..b1d34d3 100644
--- a/src/assembler_x86.h
+++ b/src/assembler_x86.h
@@ -504,8 +504,7 @@
   virtual void CopyRef(FrameOffset dest, FrameOffset src,
                        ManagedRegister scratch);
 
-  virtual void Copy(FrameOffset dest, FrameOffset src, ManagedRegister scratch,
-                    size_t size);
+  virtual void Copy(FrameOffset dest, FrameOffset src, ManagedRegister scratch, size_t size);
 
   virtual void Copy(FrameOffset dest, ManagedRegister src_base, Offset src_offset,
                     ManagedRegister scratch, size_t size);