diff --git a/src/ngx_http_lua_socket_tcp.c b/src/ngx_http_lua_socket_tcp.c
index 3ed71be370..239a6e10b2 100644
--- a/src/ngx_http_lua_socket_tcp.c
+++ b/src/ngx_http_lua_socket_tcp.c
@@ -5404,6 +5404,34 @@ ngx_http_lua_socket_tcp_setkeepalive(lua_State *L)
 
     luaL_checktype(L, 1, LUA_TTABLE);
 
+    r = ngx_http_lua_get_req(L);
+    if (r == NULL) {
+        return luaL_error(L, "no request found");
+    }
+
+    llcf = ngx_http_get_module_loc_conf(r, ngx_http_lua_module);
+
+    /* luaL_checkinteger will throw error if the argument is not a number.
+     * e.g.: bad argument \#2 to '?' (number expected, got string)
+     *
+     * We should check the argument in advance; otherwise,
+     * throwing an exception in the middle can compromise data integrity.
+     * e.g.: set pc->connection to NULL without following cleanup.
+     */
+    if (n >= 2 && !lua_isnil(L, 2)) {
+        timeout = (ngx_msec_t) luaL_checkinteger(L, 2);
+
+    } else {
+        timeout = llcf->keepalive_timeout;
+    }
+
+    if (n >= 3 && !lua_isnil(L, 3)) {
+        pool_size = luaL_checkinteger(L, 3);
+
+    } else {
+        pool_size = llcf->pool_size;
+    }
+
     lua_rawgeti(L, 1, SOCKET_CTX_INDEX);
     u = lua_touserdata(L, -1);
     lua_pop(L, 1);
@@ -5430,11 +5458,6 @@ ngx_http_lua_socket_tcp_setkeepalive(lua_State *L)
         return 2;
     }
 
-    r = ngx_http_lua_get_req(L);
-    if (r == NULL) {
-        return luaL_error(L, "no request found");
-    }
-
     if (u->request != r) {
         return luaL_error(L, "bad request");
     }
@@ -5505,18 +5528,8 @@ ngx_http_lua_socket_tcp_setkeepalive(lua_State *L)
 
     /* stack: obj timeout? size? pools cache_key */
 
-    llcf = ngx_http_get_module_loc_conf(r, ngx_http_lua_module);
-
     if (spool == NULL) {
         /* create a new socket pool for the current peer key */
-
-        if (n >= 3 && !lua_isnil(L, 3)) {
-            pool_size = luaL_checkinteger(L, 3);
-
-        } else {
-            pool_size = llcf->pool_size;
-        }
-
         if (pool_size <= 0) {
             msg = lua_pushfstring(L, "bad \"pool_size\" option value: %d",
                                   pool_size);
@@ -5580,13 +5593,6 @@ ngx_http_lua_socket_tcp_setkeepalive(lua_State *L)
         ngx_del_timer(c->write);
     }
 
-    if (n >= 2 && !lua_isnil(L, 2)) {
-        timeout = (ngx_msec_t) luaL_checkinteger(L, 2);
-
-    } else {
-        timeout = llcf->keepalive_timeout;
-    }
-
 #if (NGX_DEBUG)
     if (timeout == 0) {
         ngx_log_debug0(NGX_LOG_DEBUG_HTTP, r->connection->log, 0,
diff --git a/t/068-socket-keepalive.t b/t/068-socket-keepalive.t
index 5ca94e4b72..1660a3a361 100644
--- a/t/068-socket-keepalive.t
+++ b/t/068-socket-keepalive.t
@@ -3029,3 +3029,163 @@ connected: 1, reused: 0
 --- error_log
 lua tcp socket keepalive create connection pool for key "A"
 lua tcp socket keepalive create connection pool for key "B"
+
+
+
+=== TEST 54: wrong first argument for setkeepalive
+--- quic_max_idle_timeout: 1.2
+--- http_config eval
+    "lua_package_path '$::HtmlDir/?.lua;./?.lua;;';"
+--- config
+   server_tokens off;
+   location /t {
+        keepalive_timeout 60s;
+
+        set $port $TEST_NGINX_SERVER_PORT;
+        content_by_lua_block {
+            local port = ngx.var.port
+
+            local sock = ngx.socket.tcp()
+
+            local ok, err = sock:connect("127.0.0.1", port)
+            if not ok then
+                ngx.say("failed to connect: ", err)
+                return
+            end
+
+            ngx.say("connected: ", ok)
+
+            local req = "GET /foo HTTP/1.1\r\nHost: localhost\r\nConnection: keepalive\r\n\r\n"
+
+            local bytes, err = sock:send(req)
+            if not bytes then
+                ngx.say("failed to send request: ", err)
+                return
+            end
+
+            ngx.say("request sent: ", bytes)
+
+            local reader = sock:receiveuntil("\r\n0\r\n\r\n")
+            local data, err = reader()
+
+            if not data then
+                ngx.say("failed to receive response body: ", err)
+                return
+            end
+
+            ngx.say("received response of ", #data, " bytes")
+
+            ok, err = sock:setkeepalive()
+            if not ok then
+                ngx.say("failed to set reusable: ", err)
+            end
+
+            ok, err = sock:connect("127.0.0.1", port)
+            if not ok then
+                ngx.say("failed to connect: ", err)
+                return
+            end
+
+            ok, err = sock:setkeepalive("not a number", "not a number")
+            if not ok then
+                ngx.say("failed to set reusable: ", err)
+            end
+        }
+    }
+
+    location /foo {
+        echo foo;
+    }
+
+    location /sleep {
+        echo_sleep 1;
+    }
+--- request
+GET /t
+--- error_code:
+--- response_body
+--- error_log eval
+qr/\Qbad argument #1 to 'setkeepalive' (number expected, got string)\E/
+--- no_error_log
+[crit]
+--- timeout: 4
+
+
+
+=== TEST 55: wrong second argument for setkeepalive
+--- quic_max_idle_timeout: 1.2
+--- http_config eval
+    "lua_package_path '$::HtmlDir/?.lua;./?.lua;;';"
+--- config
+   server_tokens off;
+   location /t {
+        keepalive_timeout 60s;
+
+        set $port $TEST_NGINX_SERVER_PORT;
+        content_by_lua_block {
+            local port = ngx.var.port
+
+            local sock = ngx.socket.tcp()
+
+            local ok, err = sock:connect("127.0.0.1", port)
+            if not ok then
+                ngx.say("failed to connect: ", err)
+                return
+            end
+
+            ngx.say("connected: ", ok)
+
+            local req = "GET /foo HTTP/1.1\r\nHost: localhost\r\nConnection: keepalive\r\n\r\n"
+
+            local bytes, err = sock:send(req)
+            if not bytes then
+                ngx.say("failed to send request: ", err)
+                return
+            end
+
+            ngx.say("request sent: ", bytes)
+
+            local reader = sock:receiveuntil("\r\n0\r\n\r\n")
+            local data, err = reader()
+
+            if not data then
+                ngx.say("failed to receive response body: ", err)
+                return
+            end
+
+            ngx.say("received response of ", #data, " bytes")
+
+            ok, err = sock:setkeepalive()
+            if not ok then
+                ngx.say("failed to set reusable: ", err)
+            end
+
+            ok, err = sock:connect("127.0.0.1", port)
+            if not ok then
+                ngx.say("failed to connect: ", err)
+                return
+            end
+
+            ok, err = sock:setkeepalive(10, "not a number")
+            if not ok then
+                ngx.say("failed to set reusable: ", err)
+            end
+        }
+    }
+
+    location /foo {
+        echo foo;
+    }
+
+    location /sleep {
+        echo_sleep 1;
+    }
+--- request
+GET /t
+--- error_code:
+--- response_body
+--- error_log eval
+qr/\Qbad argument #2 to 'setkeepalive' (number expected, got string)\E/
+--- no_error_log
+[crit]
+--- timeout: 4