diff --git a/http_server.go b/http_server.go
index 0a86c28..c17844e 100644
--- a/http_server.go
+++ b/http_server.go
@@ -66,7 +66,7 @@ func (ats *Suite) StartHttpServer() {
 		}
 
 		err := ats.httpServer.ListenAndServe()
-		if !errors.Is(err, http.ErrServerClosed) {
+		if err != nil && !errors.Is(err, http.ErrServerClosed) {
 			// Error starting or closing listener:
 			logrus.Fatal("HTTP server ListenAndServe:", err)
 		}
diff --git a/smtp_server.go b/smtp_server.go
index a304629..53ba793 100644
--- a/smtp_server.go
+++ b/smtp_server.go
@@ -24,7 +24,7 @@ func (ats *Suite) StartSmtpServer() {
 		}
 
 		err := ats.smtpServer.ListenAndServe()
-		if !errors.Is(err, esmtp.ErrServerClosed) {
+		if err != nil && !errors.Is(err, esmtp.ErrServerClosed) {
 			// Error starting or closing listener:
 			logrus.Fatal("SMTP server ListenAndServe:", err)
 		}