diff --git a/internal/multiplex/mux_test.go b/internal/multiplex/mux_test.go
index 86dec41..e492305 100644
--- a/internal/multiplex/mux_test.go
+++ b/internal/multiplex/mux_test.go
@@ -65,14 +65,15 @@ func makeSessionPair(numConn int) (*Session, *Session, []*connPair) {
 
 func runEchoTest(t *testing.T, conns []net.Conn, msgLen int) {
 	var wg sync.WaitGroup
-	testData := make([]byte, msgLen)
-	rand.Read(testData)
 
 	for _, conn := range conns {
 		wg.Add(1)
 		go func(conn net.Conn) {
 			defer wg.Done()
 
+			testData := make([]byte, msgLen)
+			rand.Read(testData)
+
 			// we cannot call t.Fatalf in concurrent contexts
 			n, err := conn.Write(testData)
 			if n != msgLen {
diff --git a/internal/test/integration_test.go b/internal/test/integration_test.go
index 22935b2..e4072e0 100644
--- a/internal/test/integration_test.go
+++ b/internal/test/integration_test.go
@@ -222,14 +222,15 @@ func establishSession(lcc client.LocalConnConfig, rcc client.RemoteConnConfig, a
 
 func runEchoTest(t *testing.T, conns []net.Conn, msgLen int) {
 	var wg sync.WaitGroup
-	testData := make([]byte, msgLen)
-	rand.Read(testData)
 
 	for _, conn := range conns {
 		wg.Add(1)
 		go func(conn net.Conn) {
 			defer wg.Done()
 
+			testData := make([]byte, msgLen)
+			rand.Read(testData)
+
 			// we cannot call t.Fatalf in concurrent contexts
 			n, err := conn.Write(testData)
 			if n != msgLen {