diff --git a/spec/amqproxy/server_spec.cr b/spec/amqproxy/server_spec.cr
index bd8c4ca..3957a48 100644
--- a/spec/amqproxy/server_spec.cr
+++ b/spec/amqproxy/server_spec.cr
@@ -259,4 +259,76 @@ describe AMQProxy::Server do
       end
     end
   end
+
+  it "does not send duplicate channel.close frames when client crashes after sending close" do
+    with_server do |server, proxy_url|
+      Fiber.yield
+
+      # Open a canary connection to verify the upstream connection stays open
+      # If the bug exists, duplicate Channel::Close will close the upstream connection,
+      # affecting ALL clients sharing that connection
+      canary = AMQP::Client.new(proxy_url).connect
+      canary_channel = canary.channel
+
+      # Open multiple channels and close them rapidly, then crash
+      # This increases the probability of triggering the race condition
+      num_channels = 10
+
+      conn = AMQP::Client.new(proxy_url).connect
+      channels = (1..num_channels).map { conn.channel }
+      sleep 0.1.seconds
+      server.upstream_connections.should eq 1
+
+      # Send Channel::Close for ALL channels rapidly without waiting for CloseOk
+      channels.each do |channel|
+        conn.write AMQ::Protocol::Frame::Channel::Close.new(channel.id, 200_u16, "Normal close", 0_u16, 0_u16)
+      end
+
+      # Simulate crash: close socket abruptly WITHOUT waiting for any CloseOk
+      conn.@io.close
+
+      # Give the proxy time to process the disconnect
+      sleep 0.3.seconds
+
+      # Verify the canary connection is still alive (proves upstream connection didn't close)
+      canary.closed?.should be_false
+      canary_channel.closed?.should be_false
+      server.upstream_connections.should eq 1
+    end
+  end
+
+  it "does not send duplicate channel.close when upstream initiates close and client crashes" do
+    with_server do |server, proxy_url|
+      Fiber.yield
+
+      # Open a canary connection to verify the upstream connection stays open
+      # If the bug exists, duplicate Channel::Close will close the upstream connection,
+      # affecting ALL clients sharing that connection
+      canary = AMQP::Client.new(proxy_url).connect
+      canary_channel = canary.channel
+
+      conn = AMQP::Client.new(proxy_url).connect
+      ch = conn.channel
+      sleep 0.1.seconds
+      server.upstream_connections.should eq 1
+
+      # Trigger a channel error by consuming from non-existent queue
+      # This will cause the upstream to send Channel::Close
+      expect_raises(AMQP::Client::Channel::ClosedException) do
+        ch.basic_consume("non_existent_queue_#{rand}") { }
+      end
+
+      # Simulate client crash: close socket WITHOUT proper connection close
+      conn.@io.close
+
+      # Give the proxy time to process the disconnect
+      sleep 0.2.seconds
+
+      # Verify the canary connection is still alive (proves upstream connection didn't close)
+      # The proxy already sent CloseOk to upstream when it received Channel::Close
+      canary.closed?.should be_false
+      canary_channel.closed?.should be_false
+      server.upstream_connections.should eq 1
+    end
+  end
 end
diff --git a/src/amqproxy/client.cr b/src/amqproxy/client.cr
index ffdc8a6..26eed4e 100644
--- a/src/amqproxy/client.cr
+++ b/src/amqproxy/client.cr
@@ -8,7 +8,7 @@ module AMQProxy
   class Client
     Log = ::Log.for(self)
     getter credentials : Credentials
-    @channel_map = Hash(UInt16, UpstreamChannel?).new
+    @channel_map = Hash(UInt16, UpstreamChannel).new
     @lock = Mutex.new
     @frame_max : UInt32
     @channel_max : UInt16
@@ -74,6 +74,14 @@ module AMQProxy
           upstream_channel = channel_pool.get(DownstreamChannel.new(self, frame.channel))
           @channel_map[frame.channel] = upstream_channel
           write AMQ::Protocol::Frame::Channel::OpenOk.new(frame.channel)
+        when AMQ::Protocol::Frame::Channel::Close
+          if upstream_channel = @channel_map.delete(frame.channel)
+            # Channel was open, forward close to upstream
+            upstream_channel.write(frame)
+          else
+            # Channel doesn't exist
+            close_connection(504_u16, "CHANNEL_ERROR - Channel #{frame.channel} not open", frame)
+          end
         when AMQ::Protocol::Frame::Channel::CloseOk
           # Server closed channel, CloseOk reply to server is already sent
           @channel_map.delete(frame.channel)
@@ -148,9 +156,8 @@ module AMQProxy
         @socket.flush unless expect_more_frames?(frame)
       end
       case frame
-      when AMQ::Protocol::Frame::Channel::Close
-        @channel_map[frame.channel] = nil
-      when AMQ::Protocol::Frame::Channel::CloseOk
+      when AMQ::Protocol::Frame::Channel::Close,
+           AMQ::Protocol::Frame::Channel::CloseOk
         @channel_map.delete(frame.channel)
       when AMQ::Protocol::Frame::Connection::CloseOk
         @socket.close rescue nil
@@ -175,7 +182,7 @@ module AMQProxy
 
     private def close_all_upstream_channels(code = 500_u16, reason = "CLIENT_DISCONNECTED")
       @channel_map.each_value do |upstream_channel|
-        upstream_channel.try &.close(code, reason)
+        upstream_channel.close(code, reason)
       rescue Upstream::WriteError
         Log.debug { "Upstream write error while closing client's channels" }
         next # Nothing to do