diff --git a/src/serial.cc b/src/serial.cc
index 67336bc..40df96a 100644
--- a/src/serial.cc
+++ b/src/serial.cc
@@ -33,6 +33,11 @@ public:
     this->pimpl_->readUnlock();
   }
 private:
+  // Disable copy constructors
+  ScopedReadLock(const ScopedReadLock&);
+  void operator=(const ScopedReadLock&);
+  const ScopedReadLock& operator=(ScopedReadLock);
+
   SerialImpl *pimpl_;
 };
 
@@ -45,6 +50,10 @@ public:
     this->pimpl_->writeUnlock();
   }
 private:
+  // Disable copy constructors
+  ScopedWriteLock(const ScopedWriteLock&);
+  void operator=(const ScopedWriteLock&);
+  const ScopedWriteLock& operator=(ScopedWriteLock);
   SerialImpl *pimpl_;
 };