diff --git a/sysdeps/powerpc/fpu/s_isnan.c b/sysdeps/powerpc/fpu/s_isnan.c
index ad1d6177c5..0ad1c6241e 100644
--- a/sysdeps/powerpc/fpu/s_isnan.c
+++ b/sysdeps/powerpc/fpu/s_isnan.c
@@ -24,6 +24,9 @@
 #include "math.h"
 #include <fenv_libc.h>
 
+#undef __isnanf
+#undef isnanf
+
 int
 __isnan (x)
      double x;