diff --git a/pkg/middlewares/forwardedheaders/forwarded_header.go b/pkg/middlewares/forwardedheaders/forwarded_header.go
index 5d2355dfd..2a36859c4 100644
--- a/pkg/middlewares/forwardedheaders/forwarded_header.go
+++ b/pkg/middlewares/forwardedheaders/forwarded_header.go
@@ -104,9 +104,10 @@ func isWebsocketRequest(req *http.Request) bool {
 				return true
 			}
 
-			h = h[pos:]
+			h = h[pos+1:]
 		}
 	}
+
 	return containsHeader(connection, "upgrade") && containsHeader(upgrade, "websocket")
 }
 
diff --git a/pkg/middlewares/forwardedheaders/forwarded_header_test.go b/pkg/middlewares/forwardedheaders/forwarded_header_test.go
index 8fc290f63..40e2c323a 100644
--- a/pkg/middlewares/forwardedheaders/forwarded_header_test.go
+++ b/pkg/middlewares/forwardedheaders/forwarded_header_test.go
@@ -3,6 +3,7 @@ package forwardedheaders
 import (
 	"crypto/tls"
 	"net/http"
+	"net/http/httptest"
 	"testing"
 
 	"github.com/stretchr/testify/assert"
@@ -299,3 +300,71 @@ func TestServeHTTP(t *testing.T) {
 		})
 	}
 }
+
+func Test_isWebsocketRequest(t *testing.T) {
+	testCases := []struct {
+		desc             string
+		connectionHeader string
+		upgradeHeader    string
+		assert           assert.BoolAssertionFunc
+	}{
+		{
+			desc:             "connection Header multiple values middle",
+			connectionHeader: "foo,upgrade,bar",
+			upgradeHeader:    "websocket",
+			assert:           assert.True,
+		},
+		{
+			desc:             "connection Header multiple values end",
+			connectionHeader: "foo,bar,upgrade",
+			upgradeHeader:    "websocket",
+			assert:           assert.True,
+		},
+		{
+			desc:             "connection Header multiple values begin",
+			connectionHeader: "upgrade,foo,bar",
+			upgradeHeader:    "websocket",
+			assert:           assert.True,
+		},
+		{
+			desc:             "connection Header no upgrade",
+			connectionHeader: "foo,bar",
+			upgradeHeader:    "websocket",
+			assert:           assert.False,
+		},
+		{
+			desc:             "connection Header empty",
+			connectionHeader: "",
+			upgradeHeader:    "websocket",
+			assert:           assert.False,
+		},
+		{
+			desc:             "no header values",
+			connectionHeader: "foo,bar",
+			upgradeHeader:    "foo,bar",
+			assert:           assert.False,
+		},
+		{
+			desc:             "upgrade header multiple values",
+			connectionHeader: "upgrade",
+			upgradeHeader:    "foo,bar,websocket",
+			assert:           assert.True,
+		},
+	}
+
+	for _, test := range testCases {
+		test := test
+		t.Run(test.desc, func(t *testing.T) {
+			t.Parallel()
+
+			req := httptest.NewRequest(http.MethodGet, "http://localhost", nil)
+
+			req.Header.Set(connection, test.connectionHeader)
+			req.Header.Set(upgrade, test.upgradeHeader)
+
+			ok := isWebsocketRequest(req)
+
+			test.assert(t, ok)
+		})
+	}
+}