diff --git a/cpp/src/phonenumbers/base/basictypes.h b/cpp/src/phonenumbers/base/basictypes.h
index ed32ae9ae..865edcd22 100644
--- a/cpp/src/phonenumbers/base/basictypes.h
+++ b/cpp/src/phonenumbers/base/basictypes.h
@@ -205,7 +205,7 @@ struct CompileAssert {
 // is important for some other reason.)
 // Use like:
 //   int x ALLOW_UNUSED = ...;
-#if defined(COMPILER_GCC)
+#if defined(__GNUC__)
 #define ALLOW_UNUSED __attribute__((unused))
 #else
 #define ALLOW_UNUSED
diff --git a/tools/cpp/src/base/basictypes.h b/tools/cpp/src/base/basictypes.h
index 9d7e12c75..4b8a3988d 100644
--- a/tools/cpp/src/base/basictypes.h
+++ b/tools/cpp/src/base/basictypes.h
@@ -246,7 +246,7 @@ struct CompileAssert {
 // is important for some other reason.)
 // Use like:
 //   int x ALLOW_UNUSED = ...;
-#if defined(COMPILER_GCC)
+#if defined(__GNUC__)
 #define ALLOW_UNUSED __attribute__((unused))
 #else
 #define ALLOW_UNUSED