diff --git a/lua-mosquitto.c b/lua-mosquitto.c
index b524fed..3b6dc9d 100644
--- a/lua-mosquitto.c
+++ b/lua-mosquitto.c
@@ -193,7 +193,7 @@ static int mosq_new(lua_State *L)
 		return luaL_error(L, strerror(errno));
 	}
 
-	ctx->L = L;
+	ctx->L = NULL;
 	ctx__on_init(ctx);
 
 	luaL_getmetatable(L, MOSQ_META_CTX);
@@ -422,11 +422,13 @@ static int mosq_loop(lua_State *L, bool forever)
 	int timeout = luaL_optinteger(L, 2, -1);
 	int max_packets = luaL_optinteger(L, 3, 1);
 	int rc;
+	ctx->L = L;
 	if (forever) {
 		rc = mosquitto_loop_forever(ctx->mosq, timeout, max_packets);
 	} else {
 		rc = mosquitto_loop(ctx->mosq, timeout, max_packets);
 	}
+	ctx->L = NULL;
 	return mosq__pstatus(L, rc);
 }
 
@@ -443,8 +445,10 @@ static int ctx_loop_forever(lua_State *L)
 static int ctx_loop_start(lua_State *L)
 {
 	ctx_t *ctx = ctx_check(L, 1);
+	int rc;
 
-	int rc = mosquitto_loop_start(ctx->mosq);
+	ctx->L = L;
+	rc = mosquitto_loop_start(ctx->mosq);
 	return mosq__pstatus(L, rc);
 }
 
@@ -454,6 +458,7 @@ static int ctx_loop_stop(lua_State *L)
 	bool force = lua_toboolean(L, 2);
 
 	int rc = mosquitto_loop_stop(ctx->mosq, force);
+	ctx->L = NULL;
 	return mosq__pstatus(L, rc);
 }
 
@@ -478,8 +483,11 @@ static int ctx_loop_read(lua_State *L)
 {
 	ctx_t *ctx = ctx_check(L, 1);
 	int max_packets = luaL_optinteger(L, 2, 1);
+	int rc;
 
-	int rc = mosquitto_loop_read(ctx->mosq, max_packets);
+	ctx->L = L;
+	rc = mosquitto_loop_read(ctx->mosq, max_packets);
+	ctx->L = NULL;
 	return mosq__pstatus(L, rc);
 }
 
@@ -487,16 +495,22 @@ static int ctx_loop_write(lua_State *L)
 {
 	ctx_t *ctx = ctx_check(L, 1);
 	int max_packets = luaL_optinteger(L, 2, 1);
+	int rc;
 
-	int rc = mosquitto_loop_write(ctx->mosq, max_packets);
+	ctx->L = L;
+	rc = mosquitto_loop_write(ctx->mosq, max_packets);
+	ctx->L = NULL;
 	return mosq__pstatus(L, rc);
 }
 
 static int ctx_loop_misc(lua_State *L)
 {
 	ctx_t *ctx = ctx_check(L, 1);
+	int rc;
 
-	int rc = mosquitto_loop_misc(ctx->mosq);
+	ctx->L = L;
+	rc = mosquitto_loop_misc(ctx->mosq);
+	ctx->L = NULL;
 	return mosq__pstatus(L, rc);
 }
 
@@ -508,12 +522,9 @@ static int ctx_want_write(lua_State *L)
 	return 1;
 }
 
-static void ctx_on_connect(
-	struct mosquitto *mosq,
-	void *obj,
-	int rc)
-{
-	ctx_t *ctx = obj;
+static int ctx_on_connect_safe(lua_State *L) {
+	int ref = lua_tointeger(L, 1);
+	int rc = lua_tointeger(L, 2);
 	bool success = false;
 	char *str = "reserved for future use";
 
@@ -548,22 +559,37 @@ static void ctx_on_connect(
 			break;
 	}
 
-	lua_rawgeti(ctx->L, LUA_REGISTRYINDEX, ctx->on_connect);
+	lua_rawgeti(L, LUA_REGISTRYINDEX, ref);
 
-	lua_pushboolean(ctx->L, success);
-	lua_pushinteger(ctx->L, rc);
-	lua_pushstring(ctx->L, str);
+	lua_pushboolean(L, success);
+	lua_pushinteger(L, rc);
+	lua_pushstring(L, str);
 
-	lua_call(ctx->L, 3, 0);
-}
+	lua_call(L, 3, 0);
 
+	return 0;
+}
 
-static void ctx_on_disconnect(
+static void ctx_on_connect(
 	struct mosquitto *mosq,
 	void *obj,
 	int rc)
 {
 	ctx_t *ctx = obj;
+	lua_State *L = ctx->L;
+	lua_pushcfunction(L, ctx_on_connect_safe);
+	lua_pushinteger(L, ctx->on_connect);
+	lua_pushinteger(L, rc);
+	if (lua_pcall(L, 2, 0, 0)) {
+		/* pop error message */
+		lua_pop(L, 1);
+	}
+}
+
+
+static int ctx_on_disconnect_safe(lua_State *L) {
+	int ref = lua_tointeger(L, 1);
+	int rc = lua_tointeger(L, 2);
 	bool success = true;
 	char *str = "client-initiated disconnect";
 
@@ -572,13 +598,31 @@ static void ctx_on_disconnect(
 		str = "unexpected disconnect";
 	}
 
-	lua_rawgeti(ctx->L, LUA_REGISTRYINDEX, ctx->on_disconnect);
+	lua_rawgeti(L, LUA_REGISTRYINDEX, ref);
+
+	lua_pushboolean(L, success);
+	lua_pushinteger(L, rc);
+	lua_pushstring(L, str);
 
-	lua_pushboolean(ctx->L, success);
-	lua_pushinteger(ctx->L, rc);
-	lua_pushstring(ctx->L, str);
+	lua_call(L, 3, 0);
 
-	lua_call(ctx->L, 3, 0);
+	return 0;
+}
+
+static void ctx_on_disconnect(
+	struct mosquitto *mosq,
+	void *obj,
+	int rc)
+{
+	ctx_t *ctx = obj;
+	lua_State *L = ctx->L;
+	lua_pushcfunction(L, ctx_on_disconnect_safe);
+	lua_pushinteger(L, ctx->on_disconnect);
+	lua_pushinteger(L, rc);
+	if (lua_pcall(L, 2, 0, 0)) {
+		/* pop error message */
+		lua_pop(L, 1);
+	}
 }
 
 static void ctx_on_publish(
@@ -587,10 +631,31 @@ static void ctx_on_publish(
 	int mid)
 {
 	ctx_t *ctx = obj;
+	lua_State *L = ctx->L;
+	lua_rawgeti(L, LUA_REGISTRYINDEX, ctx->on_publish);
+	lua_pushinteger(L, mid);
+	if (lua_pcall(L, 1, 0, 0)) {
+		/* pop error message */
+		lua_pop(L, 1);
+	}
+}
+
+static int ctx_on_message_safe(lua_State *L) {
+	int ref = lua_tointeger(L, 1);
+	const struct mosquitto_message *msg = lua_touserdata(L, 2);
 
-	lua_rawgeti(ctx->L, LUA_REGISTRYINDEX, ctx->on_publish);
-	lua_pushinteger(ctx->L, mid);
-	lua_call(ctx->L, 1, 0);
+	/* push registered Lua callback function onto the stack */
+	lua_rawgeti(L, LUA_REGISTRYINDEX, ref);
+	/* push function args */
+	lua_pushinteger(L, msg->mid);
+	lua_pushstring(L, msg->topic);
+	lua_pushlstring(L, msg->payload, msg->payloadlen);
+	lua_pushinteger(L, msg->qos);
+	lua_pushboolean(L, msg->retain);
+
+	lua_call(L, 5, 0); /* args: mid, topic, payload, qos, retain */
+
+	return 0;
 }
 
 static void ctx_on_message(
@@ -599,17 +664,14 @@ static void ctx_on_message(
 	const struct mosquitto_message *msg)
 {
 	ctx_t *ctx = obj;
-
-	/* push registered Lua callback function onto the stack */
-	lua_rawgeti(ctx->L, LUA_REGISTRYINDEX, ctx->on_message);
-	/* push function args */
-	lua_pushinteger(ctx->L, msg->mid);
-	lua_pushstring(ctx->L, msg->topic);
-	lua_pushlstring(ctx->L, msg->payload, msg->payloadlen);
-	lua_pushinteger(ctx->L, msg->qos);
-	lua_pushboolean(ctx->L, msg->retain);
-
-	lua_call(ctx->L, 5, 0); /* args: mid, topic, payload, qos, retain */
+	lua_State *L = ctx->L;
+	lua_pushcfunction(L, ctx_on_message_safe);
+	lua_pushinteger(L, ctx->on_message);
+	lua_pushlightuserdata(L, (void*)msg);
+	if (lua_pcall(L, 2, 0, 0)) {
+		/* pop error message */
+		lua_pop(L, 1);
+	}
 }
 
 static void ctx_on_subscribe(
@@ -620,16 +682,24 @@ static void ctx_on_subscribe(
 	const int *granted_qos)
 {
 	ctx_t *ctx = obj;
+	lua_State *L = ctx->L;
 	int i;
 
-	lua_rawgeti(ctx->L, LUA_REGISTRYINDEX, ctx->on_subscribe);
-	lua_pushinteger(ctx->L, mid);
+	if (!lua_checkstack(L, qos_count + 2)) {
+		/* can't allocate enough stack space */
+		return;
+	}
 
+	lua_rawgeti(L, LUA_REGISTRYINDEX, ctx->on_subscribe);
+	lua_pushinteger(L, mid);
 	for (i = 0; i < qos_count; i++) {
-		lua_pushinteger(ctx->L, granted_qos[i]);
+		lua_pushinteger(L, granted_qos[i]);
 	}
 
-	lua_call(ctx->L, qos_count + 1, 0);
+	if (lua_pcall(L, qos_count + 1, 0, 0)) {
+		/* pop error message */
+		lua_pop(L, 1);
+	}
 }
 
 static void ctx_on_unsubscribe(
@@ -638,10 +708,28 @@ static void ctx_on_unsubscribe(
 	int mid)
 {
 	ctx_t *ctx = obj;
+	lua_State *L = ctx->L;
+	lua_rawgeti(L, LUA_REGISTRYINDEX, ctx->on_unsubscribe);
+	lua_pushinteger(L, mid);
+	if (lua_pcall(L, 1, 0, 0)) {
+		/* pop error message */
+		lua_pop(L, 1);
+	}
+}
+
+static int ctx_on_log_safe(lua_State *L) {
+	int ref = lua_tointeger(L, 1);
+	int level = lua_tointeger(L, 2);
+	const char *str = lua_touserdata(L, 3);
+
+	lua_rawgeti(L, LUA_REGISTRYINDEX, ref);
 
-	lua_rawgeti(ctx->L, LUA_REGISTRYINDEX, ctx->on_unsubscribe);
-	lua_pushinteger(ctx->L, mid);
-	lua_call(ctx->L, 1, 0);
+	lua_pushinteger(L, level);
+	lua_pushstring(L, str);
+
+	lua_call(L, 2, 0);
+
+	return 0;
 }
 
 static void ctx_on_log(
@@ -651,13 +739,15 @@ static void ctx_on_log(
 	const char *str)
 {
 	ctx_t *ctx = obj;
-
-	lua_rawgeti(ctx->L, LUA_REGISTRYINDEX, ctx->on_log);
-
-	lua_pushinteger(ctx->L, level);
-	lua_pushstring(ctx->L, str);
-
-	lua_call(ctx->L, 2, 0);
+	lua_State *L = ctx->L;
+	lua_pushcfunction(L, ctx_on_log_safe);
+	lua_pushinteger(L, ctx->on_log);
+	lua_pushinteger(L, level);
+	lua_pushlightuserdata(L, (void*)str);
+	if (lua_pcall(L, 3, 0, 0)) {
+		/* pop error message */
+		lua_pop(L, 1);
+	}
 }
 
 static int callback_type_from_string(const char *);