diff --git a/session_test.go b/session_test.go
index 469875b0..d7cd541e 100644
--- a/session_test.go
+++ b/session_test.go
@@ -118,7 +118,7 @@ var _ = Describe("Session", func() {
 		)
 		Expect(err).NotTo(HaveOccurred())
 		session = pSession.(*Session)
-		Expect(session.streamsMap.NumberOfStreams()).To(Equal(1)) // Crypto stream
+		Expect(session.streamsMap.openStreams).To(HaveLen(1)) // Crypto stream
 
 		cpm = &mockConnectionParametersManager{idleTime: 60 * time.Second}
 		session.connectionParameters = cpm
@@ -130,7 +130,7 @@ var _ = Describe("Session", func() {
 				StreamID: 5,
 				Data:     []byte{0xde, 0xca, 0xfb, 0xad},
 			})
-			Expect(session.streamsMap.NumberOfStreams()).To(Equal(2))
+			Expect(session.streamsMap.openStreams).To(HaveLen(2))
 			Expect(streamCallbackCalled).To(BeTrue())
 			p := make([]byte, 4)
 			str, _ := session.streamsMap.GetOrOpenStream(5)
@@ -155,14 +155,14 @@ var _ = Describe("Session", func() {
 				StreamID: 5,
 				Data:     []byte{0xde, 0xca},
 			})
-			Expect(session.streamsMap.NumberOfStreams()).To(Equal(2))
+			Expect(session.streamsMap.openStreams).To(HaveLen(2))
 			Expect(streamCallbackCalled).To(BeTrue())
 			session.handleStreamFrame(&frames.StreamFrame{
 				StreamID: 5,
 				Offset:   2,
 				Data:     []byte{0xfb, 0xad},
 			})
-			Expect(session.streamsMap.NumberOfStreams()).To(Equal(2))
+			Expect(session.streamsMap.openStreams).To(HaveLen(2))
 			p := make([]byte, 4)
 			str, _ := session.streamsMap.GetOrOpenStream(5)
 			Expect(str).ToNot(BeNil())
@@ -176,7 +176,7 @@ var _ = Describe("Session", func() {
 			Expect(err).ToNot(HaveOccurred())
 			str.Close()
 			session.garbageCollectStreams()
-			Expect(session.streamsMap.NumberOfStreams()).To(Equal(2))
+			Expect(session.streamsMap.openStreams).To(HaveLen(2))
 			str, _ = session.streamsMap.GetOrOpenStream(5)
 			Expect(str).ToNot(BeNil())
 		})
@@ -187,7 +187,7 @@ var _ = Describe("Session", func() {
 				Data:     []byte{0xde, 0xca, 0xfb, 0xad},
 				FinBit:   true,
 			})
-			Expect(session.streamsMap.NumberOfStreams()).To(Equal(2))
+			Expect(session.streamsMap.openStreams).To(HaveLen(2))
 			str, _ := session.streamsMap.GetOrOpenStream(5)
 			Expect(str).ToNot(BeNil())
 			Expect(streamCallbackCalled).To(BeTrue())
@@ -196,7 +196,7 @@ var _ = Describe("Session", func() {
 			Expect(err).To(MatchError(io.EOF))
 			Expect(p).To(Equal([]byte{0xde, 0xca, 0xfb, 0xad}))
 			session.garbageCollectStreams()
-			Expect(session.streamsMap.NumberOfStreams()).To(Equal(2))
+			Expect(session.streamsMap.openStreams).To(HaveLen(2))
 			str, _ = session.streamsMap.GetOrOpenStream(5)
 			Expect(str).ToNot(BeNil())
 		})
@@ -207,7 +207,7 @@ var _ = Describe("Session", func() {
 				Data:     []byte{0xde, 0xca, 0xfb, 0xad},
 				FinBit:   true,
 			})
-			Expect(session.streamsMap.NumberOfStreams()).To(Equal(2))
+			Expect(session.streamsMap.openStreams).To(HaveLen(2))
 			str, _ := session.streamsMap.GetOrOpenStream(5)
 			Expect(str).ToNot(BeNil())
 			Expect(streamCallbackCalled).To(BeTrue())
@@ -216,7 +216,7 @@ var _ = Describe("Session", func() {
 			Expect(err).To(MatchError(io.EOF))
 			Expect(p).To(Equal([]byte{0xde, 0xca, 0xfb, 0xad}))
 			session.garbageCollectStreams()
-			Expect(session.streamsMap.NumberOfStreams()).To(Equal(2))
+			Expect(session.streamsMap.openStreams).To(HaveLen(2))
 			str, _ = session.streamsMap.GetOrOpenStream(5)
 			Expect(str).ToNot(BeNil())
 			// We still need to close the stream locally
@@ -224,7 +224,7 @@ var _ = Describe("Session", func() {
 			// ... and simulate that we actually the FIN
 			str.sentFin()
 			session.garbageCollectStreams()
-			Expect(session.streamsMap.NumberOfStreams()).To(Equal(1))
+			Expect(session.streamsMap.openStreams).To(HaveLen(1))
 			str, err = session.streamsMap.GetOrOpenStream(5)
 			Expect(err).NotTo(HaveOccurred())
 			Expect(str).To(BeNil())
@@ -239,7 +239,7 @@ var _ = Describe("Session", func() {
 				StreamID: 5,
 				Data:     []byte{0xde, 0xca, 0xfb, 0xad},
 			})
-			Expect(session.streamsMap.NumberOfStreams()).To(Equal(2))
+			Expect(session.streamsMap.openStreams).To(HaveLen(2))
 			str, _ := session.streamsMap.GetOrOpenStream(5)
 			Expect(str).ToNot(BeNil())
 			Expect(streamCallbackCalled).To(BeTrue())
@@ -249,7 +249,7 @@ var _ = Describe("Session", func() {
 			_, err = str.Read(p)
 			Expect(err).To(MatchError(testErr))
 			session.garbageCollectStreams()
-			Expect(session.streamsMap.NumberOfStreams()).To(Equal(1))
+			Expect(session.streamsMap.openStreams).To(HaveLen(1))
 			str, err = session.streamsMap.GetOrOpenStream(5)
 			Expect(err).NotTo(HaveOccurred())
 			Expect(str).To(BeNil())
@@ -258,7 +258,7 @@ var _ = Describe("Session", func() {
 		It("closes empty streams with error", func() {
 			testErr := errors.New("test")
 			session.newStreamImpl(5)
-			Expect(session.streamsMap.NumberOfStreams()).To(Equal(2))
+			Expect(session.streamsMap.openStreams).To(HaveLen(2))
 			str, _ := session.streamsMap.GetOrOpenStream(5)
 			Expect(str).ToNot(BeNil())
 			session.closeStreamsWithError(testErr)
diff --git a/streams_map.go b/streams_map.go
index 5541b1a3..78953784 100644
--- a/streams_map.go
+++ b/streams_map.go
@@ -197,14 +197,6 @@ func (m *streamsMap) RemoveStream(id protocol.StreamID) error {
 	return nil
 }
 
-// NumberOfStreams gets the number of open streams
-func (m *streamsMap) NumberOfStreams() int {
-	m.mutex.RLock()
-	n := len(m.openStreams)
-	m.mutex.RUnlock()
-	return n
-}
-
 // garbageCollectClosedStreams deletes nil values in the streams if they are smaller than protocol.MaxNewStreamIDDelta than the highest stream opened by the client
 // note that this garbage collection is relatively expensive, since it iterates over the whole streams map. It should not be called every time a stream is openend or closed
 func (m *streamsMap) garbageCollectClosedStreams() {
diff --git a/streams_map_test.go b/streams_map_test.go
index 84f1314e..aaac8064 100644
--- a/streams_map_test.go
+++ b/streams_map_test.go
@@ -254,26 +254,6 @@ var _ = Describe("Streams Map", func() {
 		})
 	})
 
-	Context("number of streams", func() {
-		It("returns 0 in the beginning", func() {
-			Expect(m.NumberOfStreams()).To(Equal(0))
-		})
-
-		It("increases the counter when a new stream is added", func() {
-			err := m.putStream(&stream{streamID: 5})
-			Expect(err).ToNot(HaveOccurred())
-			Expect(m.NumberOfStreams()).To(Equal(1))
-		})
-
-		It("decreases the counter when removing a stream", func() {
-			err := m.putStream(&stream{streamID: 5})
-			Expect(err).ToNot(HaveOccurred())
-			err = m.RemoveStream(5)
-			Expect(err).ToNot(HaveOccurred())
-			Expect(m.NumberOfStreams()).To(BeZero())
-		})
-	})
-
 	Context("Iterate", func() {
 		// create 3 streams, ids 1 to 3
 		BeforeEach(func() {