diff --git a/Sources/NIOHTTP2/HTTP2FrameParser.swift b/Sources/NIOHTTP2/HTTP2FrameParser.swift
index 2b00aa39..23e93b0a 100644
--- a/Sources/NIOHTTP2/HTTP2FrameParser.swift
+++ b/Sources/NIOHTTP2/HTTP2FrameParser.swift
@@ -64,7 +64,12 @@ struct HTTP2FrameDecoder {
         }
 
         mutating func accumulate(bytes: inout ByteBuffer) {
-            _ = self.unusedBytes.writeBuffer(&bytes)
+            if self.unusedBytes.readableBytes == 0 {
+                self.unusedBytes = bytes
+            }
+            else {
+                _ = self.unusedBytes.writeBuffer(&bytes)
+            }
         }
     }