diff --git a/options/sign.go b/options/sign.go
index f88060c5..1bc37aeb 100644
--- a/options/sign.go
+++ b/options/sign.go
@@ -36,4 +36,8 @@ func (so *SignOptions) AddFlags(cmd *cobra.Command) {
 	cmd.Flags().StringVarP(&so.OutFilePath, "outfile", "o", "", "File to write signed data. Defaults to stdout")
 	cmd.Flags().StringVarP(&so.InFilePath, "infile", "f", "", "Witness policy file to sign")
 	cmd.Flags().StringSliceVar(&so.TimestampServers, "timestamp-servers", []string{}, "Timestamp Authority Servers to use when signing envelope")
+
+	for _, flag := range RequiredSignFlags {
+		cmd.MarkFlagRequired(flag)
+	}
 }