diff --git a/libs/bytestreamutils.h b/libs/bytestreamutils.h
index c340d544..aad7d7e4 100644
--- a/libs/bytestreamutils.h
+++ b/libs/bytestreamutils.h
@@ -22,7 +22,7 @@ Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
 #if !defined(INCLUDED_BYTESTREAMUTILS_H)
 #define INCLUDED_BYTESTREAMUTILS_H
 
-#if defined(__GCC__)
+#if defined(__GNUC__)
 
 #define	_ISOC9X_SOURCE	1
 #define _ISOC99_SOURCE	1
diff --git a/libs/math/vector.h b/libs/math/vector.h
index 777d9d38..19fdd755 100644
--- a/libs/math/vector.h
+++ b/libs/math/vector.h
@@ -49,7 +49,7 @@ inline int lrint(double f)
   return static_cast<int>(f + 0.5);
 }
 
-#elif defined(__GCC__)
+#elif defined(__GNUC__)
 
  // lrint is part of ISO C99
 #define	_ISOC9X_SOURCE	1