diff --git a/crypto/threads_pthread.c b/crypto/threads_pthread.c
index ecb53299c4..00a98f4c71 100644
--- a/crypto/threads_pthread.c
+++ b/crypto/threads_pthread.c
@@ -24,6 +24,8 @@
 #  include <unistd.h>
 #endif
 
+# include <assert.h>
+
 # ifdef PTHREAD_RWLOCK_INITIALIZER
 #  define USE_RWLOCK
 # endif