diff --git a/reg-tests/lua/set_var.lua b/reg-tests/lua/set_var.lua
new file mode 100644
index 0000000..78d1fd4
--- /dev/null
+++ b/reg-tests/lua/set_var.lua
@@ -0,0 +1,12 @@
+core.register_service("set_var", "http", function(applet)
+	local var_name = applet.headers["var"][0]
+	local result = applet:set_var(var_name, "value")
+	if result then
+		applet:set_status(202)
+	else
+		applet:set_status(400)
+	end
+	applet:add_header("echo", applet:get_var(var_name) or "(nil)")
+	applet:start_response()
+	applet:send("")
+end)
diff --git a/reg-tests/lua/set_var.vtc b/reg-tests/lua/set_var.vtc
new file mode 100644
index 0000000..2f1ba4e
--- /dev/null
+++ b/reg-tests/lua/set_var.vtc
@@ -0,0 +1,29 @@
+varnishtest "Lua: set_var"
+#REQUIRE_OPTIONS=LUA
+
+feature ignore_unknown_macro
+
+haproxy h1 -conf {
+    global
+        lua-load ${testdir}/set_var.lua
+
+    frontend fe1
+        mode http
+        ${no-htx} option http-use-htx
+        bind "fd@${fe1}"
+
+        http-request use-service lua.set_var
+} -start
+
+client c0 -connect ${h1_fe1_sock} {
+    txreq -url "/" \
+        -hdr "Var: txn.foo"
+    rxresp
+    expect resp.status == 202
+    expect resp.http.echo == "value"
+    txreq -url "/" \
+        -hdr "Var: invalid.var"
+    rxresp
+    expect resp.status == 400
+    expect resp.http.echo == "(nil)"
+} -run