diff --git a/lib/liboath/oath_key_alloc.c b/lib/liboath/oath_key_alloc.c
index 7385732..b725fb2 100644
--- a/lib/liboath/oath_key_alloc.c
+++ b/lib/liboath/oath_key_alloc.c
@@ -53,9 +53,14 @@ struct oath_key *
 oath_key_alloc(void)
 {
 	struct oath_key *key;
+	int prot, flags;
 
-	if ((key = mmap(NULL, sizeof *key, PROT_READ|PROT_WRITE,
-	    MAP_ANON|MAP_NOCORE, -1, 0)) == NULL) {
+	prot = PROT_READ|PROT_WRITE;
+	flags = MAP_ANON;
+#ifdef MAP_NOCORE
+	flags |= MAP_NOCORE;
+#endif
+	if ((key = mmap(NULL, sizeof *key, prot, flags, -1, 0)) == NULL) {
 		memset(key, 0, sizeof *key);
 		key->mapped = 1;
 		if (mlock(key, sizeof *key) == 0)