diff --git a/core/api/src/main/java/org/onlab/onos/net/flow/DefaultTrafficTreatment.java b/core/api/src/main/java/org/onlab/onos/net/flow/DefaultTrafficTreatment.java
index 7182916..269347a 100644
--- a/core/api/src/main/java/org/onlab/onos/net/flow/DefaultTrafficTreatment.java
+++ b/core/api/src/main/java/org/onlab/onos/net/flow/DefaultTrafficTreatment.java
@@ -1,19 +1,16 @@
 package org.onlab.onos.net.flow;
 
-import static org.slf4j.LoggerFactory.getLogger;
-
-import java.util.Collections;
-import java.util.LinkedList;
-import java.util.List;
-import java.util.Objects;
-
 import org.onlab.onos.net.PortNumber;
 import org.onlab.onos.net.flow.instructions.Instruction;
 import org.onlab.onos.net.flow.instructions.Instructions;
 import org.onlab.packet.IpPrefix;
 import org.onlab.packet.MacAddress;
 import org.onlab.packet.VlanId;
-import org.slf4j.Logger;
+
+import java.util.Collections;
+import java.util.LinkedList;
+import java.util.List;
+import java.util.Objects;
 
 /**
  * Default traffic treatment implementation.
@@ -58,7 +55,7 @@
         }
         if (obj instanceof DefaultTrafficTreatment) {
             DefaultTrafficTreatment that = (DefaultTrafficTreatment) obj;
-            return  Objects.equals(instructions, that.instructions);
+            return Objects.equals(instructions, that.instructions);
 
         }
         return false;
@@ -70,8 +67,6 @@
      */
     public static final class Builder implements TrafficTreatment.Builder {
 
-        private final Logger log = getLogger(getClass());
-
         boolean drop = false;
 
         List<Instruction> outputs = new LinkedList<>();
@@ -107,7 +102,8 @@
                     groups.add(instruction);
                     break;
                 default:
-                    log.warn("Unknown instruction type {}", instruction.type());
+                    throw new IllegalArgumentException("Unknown instruction type: " +
+                                                               instruction.type());
             }
             return this;
         }