diff --git a/compat/os2threads.h b/compat/os2threads.h
index b816bff15f..441ac43710 100644
--- a/compat/os2threads.h
+++ b/compat/os2threads.h
@@ -32,6 +32,8 @@
 #undef __STRICT_ANSI__          /* for _beginthread() */
 #include <stdlib.h>
 
+#include "libavutil/mem.h"
+
 typedef TID  pthread_t;
 typedef void pthread_attr_t;