diff --git a/util/oslib-posix.c b/util/oslib-posix.c
index fbd0dc8..c1bee2a 100644
--- a/util/oslib-posix.c
+++ b/util/oslib-posix.c
@@ -596,6 +596,7 @@
 void *qemu_alloc_stack(size_t *sz)
 {
     void *ptr, *guardpage;
+    int flags;
 #ifdef CONFIG_DEBUG_STACK_USAGE
     void *ptr2;
 #endif
@@ -610,8 +611,18 @@
     /* allocate one extra page for the guard page */
     *sz += pagesz;
 
-    ptr = mmap(NULL, *sz, PROT_READ | PROT_WRITE,
-               MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
+    flags = MAP_PRIVATE | MAP_ANONYMOUS;
+#if defined(MAP_STACK) && defined(__OpenBSD__)
+    /* Only enable MAP_STACK on OpenBSD. Other OS's such as
+     * Linux/FreeBSD/NetBSD have a flag with the same name
+     * but have differing functionality. OpenBSD will SEGV
+     * if it spots execution with a stack pointer pointing
+     * at memory that was not allocated with MAP_STACK.
+     */
+    flags |= MAP_STACK;
+#endif
+
+    ptr = mmap(NULL, *sz, PROT_READ | PROT_WRITE, flags, -1, 0);
     if (ptr == MAP_FAILED) {
         perror("failed to allocate memory for stack");
         abort();