diff --git a/handshake/connection_parameters_manager.go b/handshake/connection_parameters_manager.go
index 5d294815..208082ce 100644
--- a/handshake/connection_parameters_manager.go
+++ b/handshake/connection_parameters_manager.go
@@ -19,6 +19,8 @@ type ConnectionParametersManager struct {
 	params map[Tag][]byte
 	mutex  sync.RWMutex
 
+	flowControlNegotiated bool // have the flow control parameters for sending already been negotiated
+
 	maxStreamsPerConnection            uint32
 	idleConnectionStateLifetime        time.Duration
 	sendStreamFlowControlWindow        protocol.ByteCount
@@ -30,7 +32,10 @@ type ConnectionParametersManager struct {
 var errTagNotInConnectionParameterMap = errors.New("ConnectionParametersManager: Tag not found in ConnectionsParameter map")
 
 // ErrMalformedTag is returned when the tag value cannot be read
-var ErrMalformedTag = qerr.Error(qerr.InvalidCryptoMessageParameter, "malformed Tag value")
+var (
+	ErrMalformedTag                         = qerr.Error(qerr.InvalidCryptoMessageParameter, "malformed Tag value")
+	ErrFlowControlRenegotiationNotSupported = qerr.Error(qerr.InvalidCryptoMessageParameter, "renegotiation of flow control parameters not supported")
+)
 
 // NewConnectionParamatersManager creates a new connection parameters manager
 func NewConnectionParamatersManager() *ConnectionParametersManager {
@@ -66,12 +71,18 @@ func (h *ConnectionParametersManager) SetFromMap(params map[Tag][]byte) error {
 			}
 			h.idleConnectionStateLifetime = h.negotiateIdleConnectionStateLifetime(time.Duration(clientValue) * time.Second)
 		case TagSFCW:
+			if h.flowControlNegotiated {
+				return ErrFlowControlRenegotiationNotSupported
+			}
 			sendStreamFlowControlWindow, err := utils.ReadUint32(bytes.NewBuffer(value))
 			if err != nil {
 				return ErrMalformedTag
 			}
 			h.sendStreamFlowControlWindow = protocol.ByteCount(sendStreamFlowControlWindow)
 		case TagCFCW:
+			if h.flowControlNegotiated {
+				return ErrFlowControlRenegotiationNotSupported
+			}
 			sendConnectionFlowControlWindow, err := utils.ReadUint32(bytes.NewBuffer(value))
 			if err != nil {
 				return ErrMalformedTag
@@ -80,6 +91,12 @@ func (h *ConnectionParametersManager) SetFromMap(params map[Tag][]byte) error {
 		}
 	}
 
+	_, containsSFCW := params[TagSFCW]
+	_, containsCFCW := params[TagCFCW]
+	if containsCFCW || containsSFCW {
+		h.flowControlNegotiated = true
+	}
+
 	return nil
 }
 
diff --git a/handshake/connection_parameters_manager_test.go b/handshake/connection_parameters_manager_test.go
index 6a1da498..d3f8ec85 100644
--- a/handshake/connection_parameters_manager_test.go
+++ b/handshake/connection_parameters_manager_test.go
@@ -134,6 +134,23 @@ var _ = Describe("ConnectionsParameterManager", func() {
 			Expect(err).To(MatchError(ErrMalformedTag))
 			Expect(cpm.GetSendStreamFlowControlWindow()).To(Equal(protocol.InitialConnectionFlowControlWindow))
 		})
+
+		It("does not allow renegotiation of flow control parameters", func() {
+			values := map[Tag][]byte{
+				TagCFCW: {0xDE, 0xAD, 0xBE, 0xEF},
+				TagSFCW: {0xDE, 0xAD, 0xBE, 0xEF},
+			}
+			err := cpm.SetFromMap(values)
+			Expect(err).ToNot(HaveOccurred())
+			values = map[Tag][]byte{
+				TagCFCW: {0x13, 0x37, 0x13, 0x37},
+				TagSFCW: {0x13, 0x37, 0x13, 0x37},
+			}
+			err = cpm.SetFromMap(values)
+			Expect(err).To(MatchError(ErrFlowControlRenegotiationNotSupported))
+			Expect(cpm.GetSendStreamFlowControlWindow()).To(Equal(protocol.ByteCount(0xEFBEADDE)))
+			Expect(cpm.GetSendConnectionFlowControlWindow()).To(Equal(protocol.ByteCount(0xEFBEADDE)))
+		})
 	})
 
 	Context("idle connection state lifetime", func() {