diff --git a/rng/unix/mc_getrandom_stubs.c b/rng/unix/mc_getrandom_stubs.c
index c36a6335..8b80eee8 100644
--- a/rng/unix/mc_getrandom_stubs.c
+++ b/rng/unix/mc_getrandom_stubs.c
@@ -1,4 +1,6 @@
-#include <unistd.h>
+#ifndef _MSC_VER
+# include <unistd.h>
+#endif
 
 #include <caml/mlvalues.h>
 #include <caml/memory.h>
@@ -41,7 +43,7 @@ void raw_getrandom (uint8_t *data, uint32_t len) {
     if (getentropy(data + i, rlen) < 0) uerror("getentropy", Nothing);
   }
 }
-#elif (defined(__WIN32__))
+#elif (defined(__WIN32__) || defined(_WIN32))
 /* There is a choice between using RtlGenRandom and BCryptGenRandom
  * here, and Microsoft does not make the choice obvious. It appears
  * that RtlGenRandom is best used when older Windows compatibility