diff --git a/netwerk/protocol/http/nsHttpHandler.cpp b/netwerk/protocol/http/nsHttpHandler.cpp
index d1f7652f5044..cbda071ba1b7 100644
--- a/netwerk/protocol/http/nsHttpHandler.cpp
+++ b/netwerk/protocol/http/nsHttpHandler.cpp
@@ -405,6 +405,11 @@ nsHttpHandler::IsAcceptableEncoding(const char *enc)
     if (!PL_strncasecmp(enc, "x-", 2))
         enc += 2;
 
+    // gzip and deflate are inherently acceptable in modern HTTP - always
+    // process them if a stream converter can also be found.
+    if (!PL_strcasecmp(enc, "gzip") || !PL_strcasecmp(enc, "deflate"))
+        return true;
+
     return nsHttp::FindToken(mAcceptEncodings.get(), enc, HTTP_LWS ",") != nullptr;
 }