diff --git a/internal/congestion/cubic.go b/internal/congestion/cubic.go
index dcf91fc6d..8c4de76eb 100644
--- a/internal/congestion/cubic.go
+++ b/internal/congestion/cubic.go
@@ -21,7 +21,7 @@ const cubeScale = 40
 const cubeCongestionWindowScale = 410
 const cubeFactor protocol.ByteCount = 1 << cubeScale / cubeCongestionWindowScale / protocol.DefaultTCPMSS
 
-const defaultNumConnections = 2
+const defaultNumConnections = 1
 
 // Default Cubic backoff factor
 const beta float32 = 0.7
diff --git a/internal/congestion/cubic_test.go b/internal/congestion/cubic_test.go
index 52cae1456..6583e6a9f 100644
--- a/internal/congestion/cubic_test.go
+++ b/internal/congestion/cubic_test.go
@@ -24,6 +24,7 @@ var _ = Describe("Cubic", func() {
 	BeforeEach(func() {
 		clock = mockClock{}
 		cubic = NewCubic(&clock)
+		cubic.SetNumConnections(int(numConnections))
 	})
 
 	renoCwnd := func(currentCwnd protocol.ByteCount) protocol.ByteCount {