diff --git a/newlib/libm/common/s_isinf.c b/newlib/libm/common/s_isinf.c
index f22acb7f1..fe18e2aba 100644
--- a/newlib/libm/common/s_isinf.c
+++ b/newlib/libm/common/s_isinf.c
@@ -13,6 +13,8 @@
 
 #ifndef _DOUBLE_IS_32BITS
 
+#undef isinf
+
 int
 _DEFUN (isinf, (x),
 	double x)
diff --git a/newlib/libm/common/s_isnan.c b/newlib/libm/common/s_isnan.c
index 64deacd66..bc0a91631 100644
--- a/newlib/libm/common/s_isnan.c
+++ b/newlib/libm/common/s_isnan.c
@@ -190,6 +190,8 @@ QUICKREF
 
 #ifndef _DOUBLE_IS_32BITS
 
+#undef isnan
+
 #ifdef __STDC__
 	int isnan(double x)
 #else