diff --git a/newlib/libc/include/math.h b/newlib/libc/include/math.h
index dc8fe9c74..2bf35515f 100644
--- a/newlib/libc/include/math.h
+++ b/newlib/libc/include/math.h
@@ -250,7 +250,7 @@ extern double gamma _PARAMS((double));
 extern double lgamma _PARAMS((double));
 extern double erf _PARAMS((double));
 extern double erfc _PARAMS((double));
-#define log2(x) (log (x) / _M_LOG2_E)
+#define log2(x) (log (x) / _M_LOG2E)
 
 #ifndef __math_68881
 extern double hypot _PARAMS((double, double));
@@ -327,7 +327,7 @@ extern float gammaf _PARAMS((float));
 extern float lgammaf _PARAMS((float));
 extern float erff _PARAMS((float));
 extern float erfcf _PARAMS((float));
-#define log2f(x) (logf (x) / (float) _M_LOG2_E)
+#define log2f(x) (logf (x) / (float) _M_LOG2E)
 extern float hypotf _PARAMS((float, float));
 #endif /* ! defined (_REENT_ONLY) */