diff --git a/include/openvswitch/ofp-ct.h b/include/openvswitch/ofp-ct.h
index d57b6267843..ea68c2e6057 100644
--- a/include/openvswitch/ofp-ct.h
+++ b/include/openvswitch/ofp-ct.h
@@ -24,6 +24,8 @@
 
 #include "openflow/nicira-ext.h"
 
+struct ds;
+
 #ifdef __cplusplus
 extern "C" {
 #endif