diff --git a/src/main/java/org/opencord/cordvtn/api/net/PortId.java b/src/main/java/org/opencord/cordvtn/api/net/PortId.java
index 10c9e8d..4a3d36e 100644
--- a/src/main/java/org/opencord/cordvtn/api/net/PortId.java
+++ b/src/main/java/org/opencord/cordvtn/api/net/PortId.java
@@ -15,8 +15,11 @@
  */
 package org.opencord.cordvtn.api.net;
 
+import com.google.common.base.Strings;
 import org.onlab.util.Identifier;
 
+import static com.google.common.base.Preconditions.checkArgument;
+
 /**
  * Representation of the port identifier.
  */
@@ -38,6 +41,7 @@
      * @return port identifier
      */
     public static PortId of(String id) {
+        checkArgument(!Strings.isNullOrEmpty(id));
         return new PortId(id);
     }
 }