diff --git a/cmd/utils/flags.go b/cmd/utils/flags.go
index 01285015db81..98996fd7fe06 100644
--- a/cmd/utils/flags.go
+++ b/cmd/utils/flags.go
@@ -1733,27 +1733,34 @@ func SetEthConfig(ctx *cli.Context, stack *node.Node, cfg *eth.Config) {
 
 	if ctx.GlobalIsSet(EthProtocolsFlag.Name) {
 		protocolVersions := SplitAndTrim(ctx.GlobalString(EthProtocolsFlag.Name))
-		if len(protocolVersions) > 0 {
-			for _, versionString := range protocolVersions {
-				version, err := strconv.ParseUint(versionString, 10, 0)
-				if err != nil {
-					continue
-				}
+		if len(protocolVersions) == 0 {
+			Fatalf("--%s must be comma separated list of %s", EthProtocolsFlag.Name, strings.Join(strings.Fields(fmt.Sprint(eth.DefaultProtocolVersions)), ","))
+		}
 
-				isValid := false
-				for _, proto := range eth.DefaultProtocolVersions {
-					if proto == uint(version) {
-						isValid = true
-					}
-				}
+		seenVersions := map[uint]interface{}{}
+		for _, versionString := range protocolVersions {
+			version, err := strconv.ParseUint(versionString, 10, 0)
+			if err != nil {
+				Fatalf("--%s has invalid value \"%v\" with error: %v", EthProtocolsFlag.Name, versionString, err)
+			}
 
-				if !isValid {
-					Fatalf("--%s must be comma separated list of %s", EthProtocolsFlag.Name, strings.Join(strings.Fields(fmt.Sprint(eth.DefaultProtocolVersions)), ","))
+			if _, duplicate := seenVersions[uint(version)]; duplicate {
+				Fatalf("--%s has duplicate version of %v", EthProtocolsFlag.Name, versionString)
+			}
+
+			isValid := false
+			for _, proto := range eth.DefaultProtocolVersions {
+				if proto == uint(version) {
+					isValid = true
+					seenVersions[uint(version)] = nil
+					break
 				}
-				cfg.ProtocolVersions = append(cfg.ProtocolVersions, uint(version))
 			}
-		} else {
-			Fatalf("--%s must be comma separated list of %s", EthProtocolsFlag.Name, strings.Join(strings.Fields(fmt.Sprint(eth.DefaultProtocolVersions)), ","))
+
+			if !isValid {
+				Fatalf("--%s must be comma separated list of %s", EthProtocolsFlag.Name, strings.Join(strings.Fields(fmt.Sprint(eth.DefaultProtocolVersions)), ","))
+			}
+			cfg.ProtocolVersions = append(cfg.ProtocolVersions, uint(version))
 		}
 	}