Index: ports/unix/mpconfigport.h
--- ports/unix/mpconfigport.h.orig
+++ ports/unix/mpconfigport.h
@@ -95,7 +95,7 @@ typedef long mp_off_t;
 // We need to provide a declaration/definition of alloca()
 // unless support for it is disabled.
 #if !defined(MICROPY_NO_ALLOCA) || MICROPY_NO_ALLOCA == 0
-#if defined(__FreeBSD__) || defined(__NetBSD__)
+#if defined(__FreeBSD__) || defined(__NetBSD__) || defined(__OpenBSD__)
 #include <stdlib.h>
 #else
 #include <alloca.h>