diff --git a/src/libsodium/randombytes/randombytes_sysrandom.c b/src/libsodium/randombytes/randombytes_sysrandom.c
index c9852b2e..dc7ab93c 100644
--- a/src/libsodium/randombytes/randombytes_sysrandom.c
+++ b/src/libsodium/randombytes/randombytes_sysrandom.c
@@ -163,7 +163,7 @@ sysrandom_buf(void * const buf, const size_t size)
         abort();
     }
 #else
-    if (! CryptGenRandom(stream.hcrypt_prov, buf, size)) {
+    if (! CryptGenRandom(stream.hcrypt_prov, size, buf)) {
         abort();
     }
 #endif