diff --git a/proto/protocol.xml b/proto/protocol.xml
index 85aa44f..561d849 100644
--- a/proto/protocol.xml
+++ b/proto/protocol.xml
@@ -301,9 +301,19 @@
         provide information to the client on whether it was disconnected as
         part of normal operations or as result of an error on either the client
         or EIS implementation side.
+
+        A nonzero value describes an error, with the generic value "error" (1) reserved
+        as fallback.
+
+        This enum may be extended in the future, clients must be able to handle
+        values that are not in their supproted version of this enum.
       </description>
       <entry name="disconnected" value="0" help="client was purposely disconnected"/>
       <entry name="error" value="1" help="an error caused the disconnection"/>
+      <entry name="mode" value="2" help="sender/receiver client sent request for receiver/sender mode"/>
+      <entry name="protocol" value="3" help="client committed a protocol violation"/>
+      <entry name="value" value="4" help="client sent an invalid value"/>
+      <entry name="transport" value="5" help="error on the transport layer"/>
     </enum>
 
     <event name="disconnected" type="destructor" since="1">
@@ -312,11 +322,11 @@
         the client is disconnected.
 
         Where a client is disconnected by EIS on purpose, for example after
-        a user interaction, the reason is disconnect_reason.disconnected and
-        the explanation is NULL.
+        a user interaction, the reason is disconnect_reason.disconnected (i.e. zero)
+        and the explanation is NULL.
 
         Where a client is disconnected due to some invalid request or other
-        protocol error, the reason is disconnect_reason.error and
+        protocol error, the reason is one of disconnect_reason (i.e. nonzero) and
         explanation may contain a string explaining why. This string is
         intended to help debugging only and is not guaranteed to stay constant.
 
diff --git a/src/brei-shared.c b/src/brei-shared.c
index e585587..a250a22 100644
--- a/src/brei-shared.c
+++ b/src/brei-shared.c
@@ -323,10 +323,10 @@ brei_dispatch(struct brei_context *brei,
 	if (rc == -EAGAIN) {
 		return NULL;
 	} else if (rc == 0) {
-		return brei_result_new(BREI_CONNECTION_DISCONNECT_REASON_ERROR,
+		return brei_result_new(BREI_CONNECTION_DISCONNECT_REASON_TRANSPORT,
 				       "socket disconnected");
 	} else if (rc < 0) {
-		return brei_result_new(BREI_CONNECTION_DISCONNECT_REASON_ERROR,
+		return brei_result_new(BREI_CONNECTION_DISCONNECT_REASON_TRANSPORT,
 				       "error: %s", strerror(-rc));
 	}
 
@@ -367,7 +367,7 @@ brei_dispatch(struct brei_context *brei,
 		assert(interface);
 
 		if (opcode >= interface->nincoming) {
-			result = brei_result_new(BREI_CONNECTION_DISCONNECT_REASON_ERROR,
+			result = brei_result_new(BREI_CONNECTION_DISCONNECT_REASON_PROTOCOL,
 						 "opcode %u exceeds interface %s method count %u",
 						 opcode, interface->name, interface->nincoming);
 			goto error;