diff --git a/frames/stop_waiting_frame.go b/frames/stop_waiting_frame.go
index 91f937a86..5b54154ca 100644
--- a/frames/stop_waiting_frame.go
+++ b/frames/stop_waiting_frame.go
@@ -81,7 +81,7 @@ func ParseStopWaitingFrame(r *bytes.Reader, packetNumber protocol.PacketNumber,
 		return nil, err
 	}
 
-	if leastUnackedDelta > uint64(packetNumber) {
+	if leastUnackedDelta >= uint64(packetNumber) {
 		return nil, qerr.Error(qerr.InvalidStopWaitingData, "invalid LeastUnackedDelta")
 	}
 
diff --git a/frames/stop_waiting_frame_test.go b/frames/stop_waiting_frame_test.go
index b8151a28e..5a2dc2e06 100644
--- a/frames/stop_waiting_frame_test.go
+++ b/frames/stop_waiting_frame_test.go
@@ -18,13 +18,20 @@ var _ = Describe("StopWaitingFrame", func() {
 			Expect(b.Len()).To(BeZero())
 		})
 
-		It("rejects frames with an invalid LeastUnackedDelta", func() {
+		It("rejects frames that would have a negative LeastUnacked value", func() {
 			b := bytes.NewReader([]byte{0x06, 0xD})
 			_, err := ParseStopWaitingFrame(b, 10, 1, protocol.VersionWhatever)
 			Expect(err).To(HaveOccurred())
 			Expect(b.Len()).To(BeZero())
 		})
 
+		It("rejects frames that would have 0 as LeastUnacked", func() {
+			b := bytes.NewReader([]byte{0x6, 0x8})
+			_, err := ParseStopWaitingFrame(b, 8, 1, protocol.VersionWhatever)
+			Expect(err).To(HaveOccurred())
+			Expect(b.Len()).To(BeZero())
+		})
+
 		It("errors on EOFs", func() {
 			data := []byte{0x06, 0x03}
 			_, err := ParseStopWaitingFrame(bytes.NewReader(data), 5, 1, protocol.VersionWhatever)