diff --git a/libavfilter/vf_addroi.c b/libavfilter/vf_addroi.c
index de857eced4..d6765e9d8c 100644
--- a/libavfilter/vf_addroi.c
+++ b/libavfilter/vf_addroi.c
@@ -39,6 +39,7 @@ enum {
 static const char *const addroi_var_names[] = {
     "iw",
     "ih",
+    NULL,
 };
 
 typedef struct AddROIContext {