diff --git a/lib/libm/wf_lgamma.c b/lib/libm/wf_lgamma.c
index 834a4de48..4b07a7289 100644
--- a/lib/libm/wf_lgamma.c
+++ b/lib/libm/wf_lgamma.c
@@ -24,7 +24,9 @@
  */
 
 #include "fdlibm.h"
+#ifndef _IEEE_LIBM
 #define _IEEE_LIBM 1
+#endif
 
 #ifdef __STDC__
 	float lgammaf(float x)
diff --git a/lib/libm/wf_tgamma.c b/lib/libm/wf_tgamma.c
index 3ff05f331..1a6c74ca1 100644
--- a/lib/libm/wf_tgamma.c
+++ b/lib/libm/wf_tgamma.c
@@ -24,7 +24,9 @@
 
 #include "math.h"
 #include "fdlibm.h"
+#ifndef _IEEE_LIBM
 #define _IEEE_LIBM 1
+#endif
 
 #ifdef __STDC__
 	float tgammaf(float x)