diff --git a/webrtc/base/constructormagic.h b/webrtc/base/constructormagic.h
index c20be2b32f..ceee37de4b 100644
--- a/webrtc/base/constructormagic.h
+++ b/webrtc/base/constructormagic.h
@@ -11,19 +11,22 @@
 #ifndef WEBRTC_BASE_CONSTRUCTORMAGIC_H_
 #define WEBRTC_BASE_CONSTRUCTORMAGIC_H_
 
+// Undefine macros first, just in case. Some third-party includes have their own
+// version.
+
+#undef DISALLOW_ASSIGN
 #define DISALLOW_ASSIGN(TypeName) \
   void operator=(const TypeName&)
 
 // A macro to disallow the evil copy constructor and operator= functions
 // This should be used in the private: declarations for a class.
-// Undefine this, just in case. Some third-party includes have their own
-// version.
 #undef DISALLOW_COPY_AND_ASSIGN
 #define DISALLOW_COPY_AND_ASSIGN(TypeName)    \
   TypeName(const TypeName&);                    \
   DISALLOW_ASSIGN(TypeName)
 
 // Alternative, less-accurate legacy name.
+#undef DISALLOW_EVIL_CONSTRUCTORS
 #define DISALLOW_EVIL_CONSTRUCTORS(TypeName) \
   DISALLOW_COPY_AND_ASSIGN(TypeName)
 
@@ -33,6 +36,7 @@
 // This should be used in the private: declarations for a class
 // that wants to prevent anyone from instantiating it. This is
 // especially useful for classes containing only static methods.
+#undef DISALLOW_IMPLICIT_CONSTRUCTORS
 #define DISALLOW_IMPLICIT_CONSTRUCTORS(TypeName) \
   TypeName();                                    \
   DISALLOW_EVIL_CONSTRUCTORS(TypeName)