diff --git a/ktor-shared/ktor-websockets/jvm/src/io/ktor/websocket/WebSocketDeflateExtension.kt b/ktor-shared/ktor-websockets/jvm/src/io/ktor/websocket/WebSocketDeflateExtension.kt
index 62155530c0..3e41b97a60 100644
--- a/ktor-shared/ktor-websockets/jvm/src/io/ktor/websocket/WebSocketDeflateExtension.kt
+++ b/ktor-shared/ktor-websockets/jvm/src/io/ktor/websocket/WebSocketDeflateExtension.kt
@@ -173,8 +173,9 @@ public class WebSocketDeflateExtension internal constructor(
          * Configure which protocols should send the client.
          */
         public fun configureProtocols(block: (protocols: MutableList<WebSocketExtensionHeader>) -> Unit) {
+            val old = manualConfig
             manualConfig = {
-                manualConfig(it)
+                old(it)
                 block(it)
             }
         }
diff --git a/ktor-shared/ktor-websockets/jvm/test/WebSocketDeflateTest.kt b/ktor-shared/ktor-websockets/jvm/test/WebSocketDeflateTest.kt
index 1ac0ad401d..5c12043236 100644
--- a/ktor-shared/ktor-websockets/jvm/test/WebSocketDeflateTest.kt
+++ b/ktor-shared/ktor-websockets/jvm/test/WebSocketDeflateTest.kt
@@ -60,4 +60,16 @@ class WebSocketDeflateTest {
         assertEquals(extension.incomingNoContextTakeover, false)
         assertEquals(extension.outgoingNoContextTakeover, true)
     }
+
+    @Test
+    fun testManualConfig() {
+        val config = WebSocketDeflateExtension.Config()
+        config.manualConfig(mutableListOf())
+
+        config.configureProtocols {
+            it.add(WebSocketExtensionHeader("permessage-deflate", listOf("client_no_context_takeover")))
+        }
+
+        config.manualConfig(mutableListOf())
+    }
 }