diff --git a/src/hlua.c b/src/hlua.c
index 216d73a39..54d9fbcaf 100644
--- a/src/hlua.c
+++ b/src/hlua.c
@@ -9036,7 +9036,9 @@ struct task *hlua_process_task(struct task *task, void *context, unsigned int st
 		SEND_ERR(NULL, "Lua task: execution timeout.\n");
 		goto err_task_abort;
 	case HLUA_E_ERRMSG:
+		hlua_lock(hlua);
 		SEND_ERR(NULL, "Lua task: %s.\n", hlua_tostring_safe(hlua->T, -1));
+		hlua_unlock(hlua);
 		goto err_task_abort;
 	case HLUA_E_ERR:
 	default:
@@ -9311,7 +9313,9 @@ static void hlua_event_handler(struct hlua *hlua)
 		break;
 
 	case HLUA_E_ERRMSG:
+		hlua_lock(hlua);
 		SEND_ERR(NULL, "Lua event_hdl: %s.\n", hlua_tostring_safe(hlua->T, -1));
+		hlua_unlock(hlua);
 		break;
 
 	case HLUA_E_ERR:
@@ -9999,9 +10003,12 @@ static int hlua_sample_conv_wrapper(const struct arg *arg_p, struct sample *smp,
 	switch (hlua_ctx_resume(stream->hlua, 0)) {
 	/* finished. */
 	case HLUA_E_OK:
+		hlua_lock(stream->hlua);
 		/* If the stack is empty, the function fails. */
-		if (lua_gettop(stream->hlua->T) <= 0)
+		if (lua_gettop(stream->hlua->T) <= 0) {
+			hlua_unlock(stream->hlua);
 			return 0;
+		}
 
 		/* Convert the returned value in sample. */
 		hlua_lua2smp(stream->hlua->T, -1, smp);
@@ -10010,6 +10017,7 @@ static int hlua_sample_conv_wrapper(const struct arg *arg_p, struct sample *smp,
 		 */
 		smp_dup(smp);
 		lua_pop(stream->hlua->T, 1);
+		hlua_unlock(stream->hlua);
 		return 1;
 
 	/* yield. */
@@ -10020,9 +10028,11 @@ static int hlua_sample_conv_wrapper(const struct arg *arg_p, struct sample *smp,
 	/* finished with error. */
 	case HLUA_E_ERRMSG:
 		/* Display log. */
+		hlua_lock(stream->hlua);
 		SEND_ERR(stream->be, "Lua converter '%s': %s.\n",
 		         fcn->name, hlua_tostring_safe(stream->hlua->T, -1));
 		lua_pop(stream->hlua->T, 1);
+		hlua_unlock(stream->hlua);
 		return 0;
 
 	case HLUA_E_ETMOUT:
@@ -10124,9 +10134,12 @@ static int hlua_sample_fetch_wrapper(const struct arg *arg_p, struct sample *smp
 	switch (hlua_ctx_resume(stream->hlua, 0)) {
 	/* finished. */
 	case HLUA_E_OK:
+		hlua_lock(stream->hlua);
 		/* If the stack is empty, the function fails. */
-		if (lua_gettop(stream->hlua->T) <= 0)
+		if (lua_gettop(stream->hlua->T) <= 0) {
+			hlua_unlock(stream->hlua);
 			return 0;
+		}
 
 		/* Convert the returned value in sample. */
 		hlua_lua2smp(stream->hlua->T, -1, smp);
@@ -10135,6 +10148,7 @@ static int hlua_sample_fetch_wrapper(const struct arg *arg_p, struct sample *smp
 		 */
 		smp_dup(smp);
 		lua_pop(stream->hlua->T, 1);
+		hlua_unlock(stream->hlua);
 
 		/* Set the end of execution flag. */
 		smp->flags &= ~SMP_F_MAY_CHANGE;
@@ -10148,9 +10162,11 @@ static int hlua_sample_fetch_wrapper(const struct arg *arg_p, struct sample *smp
 	/* finished with error. */
 	case HLUA_E_ERRMSG:
 		/* Display log. */
+		hlua_lock(stream->hlua);
 		SEND_ERR(smp->px, "Lua sample-fetch '%s': %s.\n",
 		         fcn->name, hlua_tostring_safe(stream->hlua->T, -1));
 		lua_pop(stream->hlua->T, 1);
+		hlua_unlock(stream->hlua);
 		return 0;
 
 	case HLUA_E_ETMOUT:
@@ -10460,8 +10476,10 @@ static enum act_return hlua_action(struct act_rule *rule, struct proxy *px,
 	/* finished. */
 	case HLUA_E_OK:
 		/* Catch the return value */
+		hlua_lock(s->hlua);
 		if (lua_gettop(s->hlua->T) > 0)
 			act_ret = lua_tointeger(s->hlua->T, -1);
+		hlua_unlock(s->hlua);
 
 		/* Set timeout in the required channel. */
 		if (act_ret == ACT_RET_YIELD) {
@@ -10501,9 +10519,11 @@ static enum act_return hlua_action(struct act_rule *rule, struct proxy *px,
 	/* finished with error. */
 	case HLUA_E_ERRMSG:
 		/* Display log. */
+		hlua_lock(s->hlua);
 		SEND_ERR(px, "Lua function '%s': %s.\n",
 		         rule->arg.hlua_rule->fcn->name, hlua_tostring_safe(s->hlua->T, -1));
 		lua_pop(s->hlua->T, 1);
+		hlua_unlock(s->hlua);
 		goto end;
 
 	case HLUA_E_ETMOUT:
@@ -10678,9 +10698,11 @@ void hlua_applet_tcp_fct(struct appctx *ctx)
 	/* finished with error. */
 	case HLUA_E_ERRMSG:
 		/* Display log. */
+		hlua_lock(hlua);
 		SEND_ERR(px, "Lua applet tcp '%s': %s.\n",
 		         rule->arg.hlua_rule->fcn->name, hlua_tostring_safe(hlua->T, -1));
 		lua_pop(hlua->T, 1);
+		hlua_unlock(hlua);
 		goto error;
 
 	case HLUA_E_ETMOUT:
@@ -10889,9 +10911,11 @@ void hlua_applet_http_fct(struct appctx *ctx)
 		/* finished with error. */
 		case HLUA_E_ERRMSG:
 			/* Display log. */
+			hlua_lock(hlua);
 			SEND_ERR(px, "Lua applet http '%s': %s.\n",
 				 rule->arg.hlua_rule->fcn->name, hlua_tostring_safe(hlua->T, -1));
 			lua_pop(hlua->T, 1);
+			hlua_unlock(hlua);
 			goto error;
 
 		case HLUA_E_ETMOUT:
@@ -11515,9 +11539,11 @@ static int hlua_cli_io_handler_fct(struct appctx *appctx)
 	/* finished with error. */
 	case HLUA_E_ERRMSG:
 		/* Display log. */
+		hlua_lock(hlua);
 		SEND_ERR(NULL, "Lua cli '%s': %s.\n",
 		         fcn->name, hlua_tostring_safe(hlua->T, -1));
 		lua_pop(hlua->T, 1);
+		hlua_unlock(hlua);
 		return 1;
 
 	case HLUA_E_ETMOUT:
@@ -11928,9 +11954,25 @@ static int hlua_filter_new(struct stream *s, struct filter *filter)
 
 	switch (hlua_ctx_resume(s->hlua, 0)) {
 	case HLUA_E_OK:
+		/* The following Lua calls can fail. */
+		if (!SET_SAFE_LJMP(s->hlua)) {
+			const char *error;
+
+			hlua_lock(s->hlua);
+			if (lua_type(s->hlua->T, -1) == LUA_TSTRING)
+				error = hlua_tostring_safe(s->hlua->T, -1);
+			else
+				error = "critical error";
+			SEND_ERR(s->be, "Lua filter '%s': %s.\n", conf->reg->name, error);
+			hlua_unlock(s->hlua);
+			ret = 0;
+			goto end;
+		}
+
 		/* Nothing returned or not a table, ignore the filter for current stream */
 		if (!lua_gettop(s->hlua->T) || !lua_istable(s->hlua->T, 1)) {
 			ret = 0;
+			RESET_SAFE_LJMP(s->hlua);
 			goto end;
 		}
 
@@ -11942,6 +11984,10 @@ static int hlua_filter_new(struct stream *s, struct filter *filter)
 		/* Save a ref on the filter ctx */
 		lua_pushvalue(s->hlua->T, 1);
 		flt_ctx->ref = hlua_ref(s->hlua->T);
+
+		/* At this point the execution is safe. */
+		RESET_SAFE_LJMP(s->hlua);
+
 		filter->ctx = flt_ctx;
 		break;
 	case HLUA_E_ERRMSG:
@@ -12106,10 +12152,12 @@ static int hlua_filter_callback(struct stream *s, struct filter *filter, const c
 	switch (hlua_ctx_resume(flt_hlua, !(flags & HLUA_FLT_CB_FINAL))) {
 	case HLUA_E_OK:
 		/* Catch the return value if it required */
+		hlua_lock(flt_hlua);
 		if ((flags & HLUA_FLT_CB_RETVAL) && lua_gettop(flt_hlua->T) > 0) {
 			ret = lua_tointeger(flt_hlua->T, -1);
 			lua_settop(flt_hlua->T, 0); /* Empty the stack. */
 		}
+		hlua_unlock(flt_hlua);
 
 		/* Set timeout in the required channel. */
 		if (flt_hlua->wake_time != TICK_ETERNITY) {
@@ -12138,7 +12186,9 @@ static int hlua_filter_callback(struct stream *s, struct filter *filter, const c
 		ret = 0;
 		goto end;
 	case HLUA_E_ERRMSG:
+		hlua_lock(flt_hlua);
 		SEND_ERR(s->be, "Lua filter '%s' : %s.\n", conf->reg->name, hlua_tostring_safe(flt_hlua->T, -1));
+		hlua_unlock(flt_hlua);
 		ret = -1;
 		goto end;
 	case HLUA_E_ETMOUT: