diff --git a/imapclient/cmds.go b/imapclient/cmds.go
index 68888e4..4b2a88d 100644
--- a/imapclient/cmds.go
+++ b/imapclient/cmds.go
@@ -150,10 +150,6 @@ func (c *Conn) AuthenticateSCRAM(method string, h func() hash.Hash, username, pa
 func (c *Conn) CompressDeflate() (untagged []Untagged, result Result, rerr error) {
 	defer c.recover(&rerr)
 
-	if _, ok := c.CapAvailable[CapCompressDeflate]; !ok {
-		c.xerrorf("server does not implement capability %s", CapCompressDeflate)
-	}
-
 	untagged, result, rerr = c.Transactf("compress deflate")
 	c.xcheck(rerr)
 
diff --git a/imapserver/server.go b/imapserver/server.go
index 80102f8..366e988 100644
--- a/imapserver/server.go
+++ b/imapserver/server.go
@@ -174,7 +174,9 @@ var authFailDelay = time.Second  // After authentication failure.
 // TLS. The client should not be selecting PLUS variants on non-TLS connections,
 // instead opting to do the bare SCRAM variant without indicating the server claims
 // to support the PLUS variant (skipping the server downgrade detection check).
-const serverCapabilities = "IMAP4rev2 IMAP4rev1 ENABLE LITERAL+ IDLE SASL-IR BINARY UNSELECT UIDPLUS ESEARCH SEARCHRES MOVE UTF8=ACCEPT LIST-EXTENDED SPECIAL-USE CREATE-SPECIAL-USE LIST-STATUS AUTH=SCRAM-SHA-256-PLUS AUTH=SCRAM-SHA-256 AUTH=SCRAM-SHA-1-PLUS AUTH=SCRAM-SHA-1 AUTH=CRAM-MD5 ID APPENDLIMIT=9223372036854775807 CONDSTORE QRESYNC STATUS=SIZE QUOTA QUOTA=RES-STORAGE METADATA SAVEDATE WITHIN NAMESPACE COMPRESS=DEFLATE LIST-METADATA MULTIAPPEND REPLACE"
+const serverCapabilities = "IMAP4rev2 IMAP4rev1 ENABLE LITERAL+ IDLE SASL-IR BINARY UNSELECT UIDPLUS ESEARCH SEARCHRES MOVE UTF8=ACCEPT LIST-EXTENDED SPECIAL-USE CREATE-SPECIAL-USE LIST-STATUS AUTH=SCRAM-SHA-256-PLUS AUTH=SCRAM-SHA-256 AUTH=SCRAM-SHA-1-PLUS AUTH=SCRAM-SHA-1 AUTH=CRAM-MD5 ID APPENDLIMIT=9223372036854775807 CONDSTORE QRESYNC STATUS=SIZE QUOTA QUOTA=RES-STORAGE METADATA SAVEDATE WITHIN NAMESPACE LIST-METADATA MULTIAPPEND REPLACE"
+
+// disabled: COMPRESS=DEFLATE, has interoperability issues. The flate reader (inflate) still blocks on partial flushes, preventing progress.
 
 type conn struct {
 	cid               int64
diff --git a/rfc/index.txt b/rfc/index.txt
index 23b770d..17d83ee 100644
--- a/rfc/index.txt
+++ b/rfc/index.txt
@@ -189,7 +189,7 @@ https://www.iana.org/assignments/message-headers/message-headers.xhtml
 4551	Yes	Obs	(RFC 7162) IMAP Extension for Conditional STORE Operation or Quick Flag Changes Resynchronization
 4731	Yes	-	IMAP4 Extension to SEARCH Command for Controlling What Kind of Information Is Returned
 4959	Yes	-	IMAP Extension for Simple Authentication and Security Layer (SASL) Initial Client Response
-4978	Yes	-	The IMAP COMPRESS Extension
+4978	Roadmap	-	The IMAP COMPRESS Extension
 5032	Yes	-	WITHIN Search Extension to the IMAP Protocol
 5092	Roadmap	-	IMAP URL Scheme
 5161	Yes	-	The IMAP ENABLE Extension