diff --git a/cmd/serve.go b/cmd/serve.go
index 914a9fc..63119b9 100644
--- a/cmd/serve.go
+++ b/cmd/serve.go
@@ -9,6 +9,7 @@ import (
 	"heckel.io/ntfy/util"
 	"log"
 	"math"
+	"strings"
 	"time"
 )
 
@@ -123,6 +124,8 @@ func execServe(c *cli.Context) error {
 		return errors.New("if smtp-server-listen is set, smtp-server-domain must also be set")
 	} else if attachmentCacheDir != "" && baseURL == "" {
 		return errors.New("if attachment-cache-dir is set, base-url must also be set")
+	} else if baseURL != "" && (strings.HasPrefix(baseURL, "http://") || strings.HasPrefix(baseURL, "https://")) {
+		return errors.New("if set, base-url must start with http:// or https://")
 	}
 
 	// Special case: Unset default