diff --git a/src/evalfunc.c b/src/evalfunc.c
index 3e020bc..bdfd632 100644
--- a/src/evalfunc.c
+++ b/src/evalfunc.c
@@ -277,6 +277,15 @@
 }
 
 /*
+ * Check "type" is an object.
+ */
+    static int
+arg_object(type_T *type, type_T *decl_type UNUSED, argcontext_T *context)
+{
+    return check_arg_type(&t_object, type, context);
+}
+
+/*
  * Check "type" is a dict of 'any'.
  */
     static int
@@ -745,6 +754,20 @@
 }
 
 /*
+ * Check "type" is a list of 'any' or a class.
+ */
+    static int
+arg_class_or_list(type_T *type, type_T *decl_type UNUSED, argcontext_T *context)
+{
+    if (type->tt_type == VAR_CLASS
+	    || type->tt_type == VAR_LIST
+	    || type_any_or_unknown(type))
+	return OK;
+    arg_type_mismatch(&t_class, type, context->arg_idx + 1);
+    return FAIL;
+}
+
+/*
  * Check "type" is a list of 'any' or a blob or a string.
  */
     static int
@@ -1125,6 +1148,7 @@
 static argcheck_T arg3_libcall[] = {arg_string, arg_string, arg_string_or_nr};
 static argcheck_T arg14_maparg[] = {arg_string, arg_string, arg_bool, arg_bool};
 static argcheck_T arg2_filter[] = {arg_list_or_dict_or_blob_or_string_mod, arg_filter_func};
+static argcheck_T arg2_instanceof[] = {arg_object, arg_class_or_list};
 static argcheck_T arg2_map[] = {arg_list_or_dict_or_blob_or_string_mod, arg_map_func};
 static argcheck_T arg2_mapnew[] = {arg_list_or_dict_or_blob_or_string, NULL};
 static argcheck_T arg25_matchadd[] = {arg_string, arg_string, arg_number, arg_number, arg_dict_any};
@@ -2124,6 +2148,8 @@
 			ret_string,	    f_inputsecret},
     {"insert",		2, 3, FEARG_1,	    arg23_insert,
 			ret_first_arg,	    f_insert},
+    {"instanceof",	2, 2, FEARG_1,	    arg2_instanceof,
+			ret_bool,	    f_instanceof},
     {"interrupt",	0, 0, 0,	    NULL,
 			ret_void,	    f_interrupt},
     {"invert",		1, 1, FEARG_1,	    arg1_number,