diff --git a/Makefile b/Makefile
index 47e882f..7342731 100644
--- a/Makefile
+++ b/Makefile
@@ -16,8 +16,8 @@ fmt: ## Run go fmt against code
 	go fmt ./...
 
 .PHONY: tests
-tests: ## Run all tests and requires a running rabbitmq-server
-	go test -cpu 1,2 -race -v -tags integration
+tests: ## Run all tests and requires a running rabbitmq-server. Use GO_TEST_FLAGS to add extra flags to go test
+	go test -race -v -tags integration $(GO_TEST_FLAGS)
 
 .PHONY: check
 check:
diff --git a/connection.go b/connection.go
index e01d835..23f1832 100644
--- a/connection.go
+++ b/connection.go
@@ -912,6 +912,9 @@ func (c *Connection) openTune(config Config, auth Authentication) error {
 		return ErrCredentials
 	}
 
+	// Edge case that may race with c.shutdown()
+	// https://github.com/rabbitmq/amqp091-go/issues/170
+	c.m.Lock()
 	// When the server and client both use default 0, then the max channel is
 	// only limited by uint16.
 	c.Config.ChannelMax = pick(config.ChannelMax, int(tune.ChannelMax))
@@ -919,6 +922,7 @@ func (c *Connection) openTune(config Config, auth Authentication) error {
 		c.Config.ChannelMax = defaultChannelMax
 	}
 	c.Config.ChannelMax = min(c.Config.ChannelMax, maxChannelMax)
+	c.m.Unlock()
 
 	// Frame size includes headers and end byte (len(payload)+8), even if
 	// this is less than FrameMinSize, use what the server sends because the
@@ -974,7 +978,9 @@ func (c *Connection) openComplete() error {
 		_ = deadliner.SetDeadline(time.Time{})
 	}
 
+	c.m.Lock()
 	c.allocator = newAllocator(1, c.Config.ChannelMax)
+	c.m.Unlock()
 	return nil
 }