diff --git a/libavfilter/vf_addroi.c b/libavfilter/vf_addroi.c
index dd3daeda81..2a9f3e5cdf 100644
--- a/libavfilter/vf_addroi.c
+++ b/libavfilter/vf_addroi.c
@@ -38,6 +38,7 @@ enum {
 static const char *const addroi_var_names[] = {
     "iw",
     "ih",
+    NULL,
 };
 
 typedef struct AddROIContext {