diff --git a/src/proto/blob.pro b/src/proto/blob.pro
index 7c8b5ac..06959aa 100644
--- a/src/proto/blob.pro
+++ b/src/proto/blob.pro
@@ -20,7 +20,7 @@
 int blob_set_range(blob_T *dest, long n1, long n2, typval_T *src);
 void blob_add(typval_T *argvars, typval_T *rettv);
 void blob_remove(typval_T *argvars, typval_T *rettv, char_u *arg_errmsg);
-void blob_filter_map(blob_T *blob_arg, filtermap_T filtermap, typval_T *expr, typval_T *rettv);
+void blob_filter_map(blob_T *blob_arg, filtermap_T filtermap, typval_T *expr, char_u *arg_errmsg, typval_T *rettv);
 void blob_insert_func(typval_T *argvars, typval_T *rettv);
 void blob_reduce(typval_T *argvars, typval_T *expr, typval_T *rettv);
 void blob_reverse(blob_T *b, typval_T *rettv);