diff --git a/libm/include/complex.h b/libm/include/complex.h
index c975a096..89465e8b 100644
--- a/libm/include/complex.h
+++ b/libm/include/complex.h
@@ -10,6 +10,10 @@
 
 #include <features.h>
 
+#ifndef __sortix_libm__
+#define __sortix_libm__ 1
+#endif
+
 #define complex _Complex
 #define _Complex_I 1.0fi
 #define I _Complex_I
diff --git a/libm/include/fenv.h b/libm/include/fenv.h
index 4668be44..01cbf321 100644
--- a/libm/include/fenv.h
+++ b/libm/include/fenv.h
@@ -29,6 +29,11 @@
 #define INCLUDE_FENV_H
 
 #include <features.h>
+
+#ifndef __sortix_libm__
+#define __sortix_libm__ 1
+#endif
+
 #include <machine/fenv.h>
 
 __BEGIN_DECLS
diff --git a/libm/include/ieee754.h b/libm/include/ieee754.h
index 7ee89279..7361f070 100644
--- a/libm/include/ieee754.h
+++ b/libm/include/ieee754.h
@@ -27,6 +27,11 @@
 #define INCLUDE_IEEE754_H
 
 #include <features.h>
+
+#ifndef __sortix_libm__
+#define __sortix_libm__ 1
+#endif
+
 #include <endian.h>
 
 /* glibc compatibility */
diff --git a/libm/include/ieeefp.h b/libm/include/ieeefp.h
index 38bd29c5..00cf1657 100644
--- a/libm/include/ieeefp.h
+++ b/libm/include/ieeefp.h
@@ -10,6 +10,10 @@
 
 #include <features.h>
 
+#ifndef __sortix_libm__
+#define __sortix_libm__ 1
+#endif
+
 #include <machine/fenv.h>
 
 __BEGIN_DECLS
diff --git a/libm/include/math.h b/libm/include/math.h
index de38446c..ce9d2c70 100644
--- a/libm/include/math.h
+++ b/libm/include/math.h
@@ -28,6 +28,10 @@
 
 #include <features.h>
 
+#ifndef __sortix_libm__
+#define __sortix_libm__ 1
+#endif
+
 #if defined(__sortix__)
 #include <__/limits.h>
 #include <__/wordsize.h>
diff --git a/libm/include/tgmath.h b/libm/include/tgmath.h
index acffd1f6..2798e10b 100644
--- a/libm/include/tgmath.h
+++ b/libm/include/tgmath.h
@@ -30,6 +30,12 @@
 #ifndef INCLUDE_TGMATH_H
 #define INCLUDE_TGMATH_H
 
+#include <features.h>
+
+#ifndef __sortix_libm__
+#define __sortix_libm__ 1
+#endif
+
 #include <math.h>
 #include <complex.h>