diff --git a/project/cli.go b/project/cli.go
index 099c93a..f825b04 100644
--- a/project/cli.go
+++ b/project/cli.go
@@ -69,8 +69,9 @@ var peerBlockCmd = &cobra.Command{
 	Use:   "block",
 	Short: "Block a peer from your local node.",
 	Run: func(cmd *cobra.Command, args []string) {
-		mhash := args[0]
-		fmt.Printf("TODO: Validate this input string %s\n", mhash)
+		mHash := validateMhash(args[0])
+		addPeer(mHash, blocked)
+		fmt.Printf("Blocked %s\n", mHash)
 	},
 }
 
diff --git a/project/decoders.go b/project/decoders.go
index ebb54de..ea8f0fb 100644
--- a/project/decoders.go
+++ b/project/decoders.go
@@ -1,7 +1,8 @@
 package main
 
 import (
-	"fmt"
+	"log"
+	"strings"
 )
 
 type testCase struct {
@@ -14,9 +15,22 @@ type testCase struct {
 func B32Decode(input string) []byte {
 	output, error := encoder.DecodeString(input)
 	if error != nil {
-		msg := fmt.Sprintf("Error decoding Base32 string %s", input)
-		panic(msg)
+		log.Fatalf("Error decoding Base32 string %s", input)
 	}
 
 	return output
 }
+
+func validateMhash(input string) string {
+	arry := strings.Split(input, ".")
+	if len(arry) != 2 {
+		log.Fatalf("Expected '%s' to be an mHash", input)
+	}
+	switch arry[0] + "." {
+	case BlobSigil, MessageSigil, PeerSigil:
+		return input
+	}
+	msg := "Expected left side of Mhash dot to be one of %s, %s, %s. Got: %s"
+	log.Fatalf(msg, BlobSigil, MessageSigil, PeerSigil, arry[0])
+	return input
+}
diff --git a/project/peers.go b/project/peers.go
index b81c650..68c6340 100644
--- a/project/peers.go
+++ b/project/peers.go
@@ -39,7 +39,7 @@ func addPeer(mHash string, status PeerStatus) {
 	}
 	_, err2 := tx.Exec(createPeer, mHash, status)
 	if err2 != nil {
-		log.Fatalf("Failed to addPeer (1): %s", err2)
+		log.Fatalf("Failure. Possible duplicate peer?: %s", err2)
 	}
 	err1 := tx.Commit()
 	if err1 != nil {