diff --git a/Sources/WebMIDIKit/MIDIPortMap.swift b/Sources/WebMIDIKit/MIDIPortMap.swift
index 3bdb1c5..88e9688 100644
--- a/Sources/WebMIDIKit/MIDIPortMap.swift
+++ b/Sources/WebMIDIKit/MIDIPortMap.swift
@@ -57,7 +57,7 @@ public class MIDIPortMap<Value: MIDIPort>: Collection {
         if port.isVirtual {
             return self[port.id]!
         } else {
-            assert(self[port.id] == nil)
+            assert(self[port.id] == nil, "Port with ID \(port.id) should not exist, yet")
             self[port.id] = port
             return port
         }
@@ -66,8 +66,7 @@ public class MIDIPortMap<Value: MIDIPort>: Collection {
 
     internal final func remove(_ endpoint: MIDIEndpoint) -> Value? {
         // disconnect?
-        guard let port = self[endpoint] else { assert(false); return nil }
-        assert(port.state == .connected)
+        guard let port = self[endpoint] else { return nil }
         self[port.id] = nil
         return port
     }