diff --git a/include/Makefile.am b/include/Makefile.am
index d4487d7..4811145 100644
--- a/include/Makefile.am
+++ b/include/Makefile.am
@@ -7,4 +7,5 @@ noinst_HEADERS += stdlib.h
 noinst_HEADERS += string.h
 noinst_HEADERS += unistd.h
 noinst_HEADERS += machine/endian.h
+noinst_HEADERS += sys/mman.h
 noinst_HEADERS += sys/types.h
diff --git a/include/sys/mman.h b/include/sys/mman.h
new file mode 100644
index 0000000..37d36d8
--- /dev/null
+++ b/include/sys/mman.h
@@ -0,0 +1,14 @@
+#include_next <sys/mman.h>
+
+#ifndef LIBCRYPTOCOMPAT_MMAN_H
+#define LIBCRYPTOCOMPAT_MMAN_H
+
+#ifndef MAP_ANONYMOUS
+#ifdef MAP_ANON
+#define MAP_ANONYMOUS MAP_ANON
+#else
+#error "System does not support mapping anonymous pages?"
+#endif
+#endif
+
+#endif