diff --git a/cmd/multiplicativeOrder.go b/cmd/multiplicativeOrder.go
index a47a5b1..86f4d17 100644
--- a/cmd/multiplicativeOrder.go
+++ b/cmd/multiplicativeOrder.go
@@ -38,6 +38,11 @@ func multiplicativeOrder(cmd *cobra.Command, args []string) {
 		cobra.CheckErr("invalid modulus " + multiplicativeOrderModulus)
 	}
 
+	gcd := new(big.Int).GCD(nil, nil, g, m)
+	if gcd.Cmp(big.NewInt(1)) != 0 {
+		cobra.CheckErr("base " + multiplicativeOrderBase + " and modulus " + multiplicativeOrderModulus + " are not coprime")
+	}
+
 	k := lib.MultiplicativeOrder(g, m)
 	fmt.Println(k)
 }