diff --git a/ff-unitxc-converter/src/main/java/net/forwardfire/unitxc/config/builder/UnitXCTypeCompoundExponentBuilder.java b/ff-unitxc-converter/src/main/java/net/forwardfire/unitxc/config/builder/UnitXCTypeCompoundExponentBuilder.java
index 5162a5b..1d0fefb 100644
--- a/ff-unitxc-converter/src/main/java/net/forwardfire/unitxc/config/builder/UnitXCTypeCompoundExponentBuilder.java
+++ b/ff-unitxc-converter/src/main/java/net/forwardfire/unitxc/config/builder/UnitXCTypeCompoundExponentBuilder.java
@@ -49,6 +49,7 @@ public class UnitXCTypeCompoundExponentBuilder extends AbstractUnitXCBuilder<Uni
 		super(parent,new Object(), (p,v) -> {});
 		this.unitGroupId = unitGroupId;
 		this.exponent = exponent;
+		UnitXCGroup model = parent.getValue();
 		parent.getValue().setTypeGenerator(new UnitXCTypeGenerator() {
 			
 			UnitXCGroup getGroup() {
@@ -82,8 +83,24 @@ public class UnitXCTypeCompoundExponentBuilder extends AbstractUnitXCBuilder<Uni
 				};
 			}
 			
+			public UnitXCType getUnitTypeAlias(String id) {
+				for (UnitXCType type:model.getUnitTypes()) {
+					if (type.getId().equals(id)) {
+						return type;
+					}
+					if (type.getName().equals(id)) {
+						return type;
+					}
+				}
+				return null;
+			}
+			
 			@Override
 			public UnitXCType getUnitType(String id) {
+				UnitXCType al = getUnitTypeAlias(id);
+				if (al != null) {
+					return al;
+				}
 				if (!id.endsWith(unitIdPostfix)) {
 					return null;
 				}
diff --git a/ff-unitxc-converter/src/main/java/net/forwardfire/unitxc/converter/UnitXConverter.java b/ff-unitxc-converter/src/main/java/net/forwardfire/unitxc/converter/UnitXConverter.java
index 2344e65..e2eecd6 100644
--- a/ff-unitxc-converter/src/main/java/net/forwardfire/unitxc/converter/UnitXConverter.java
+++ b/ff-unitxc-converter/src/main/java/net/forwardfire/unitxc/converter/UnitXConverter.java
@@ -50,7 +50,7 @@ public class UnitXConverter {
 	}
 	
 	private UnitXCType getUnitType(String id) {
-		return unitManager.getUnitType(id);
+		return Validate.notNull(unitManager.getUnitType(id),"Could not resolve unit type for id; '"+id+"'");
 	}
 	
 	public double convert(double value, String fromTypeId, String toTypeId) {
diff --git a/ff-unitxc-converter/src/main/java/net/forwardfire/unitxc/converter/UnitXConverterEngine.java b/ff-unitxc-converter/src/main/java/net/forwardfire/unitxc/converter/UnitXConverterEngine.java
index b5f7718..8e719bb 100644
--- a/ff-unitxc-converter/src/main/java/net/forwardfire/unitxc/converter/UnitXConverterEngine.java
+++ b/ff-unitxc-converter/src/main/java/net/forwardfire/unitxc/converter/UnitXConverterEngine.java
@@ -66,6 +66,18 @@ public final class UnitXConverterEngine {
 	}
 	
 	public UnitXConverterResult convertStepped(BigDecimal valueConvert2,UnitXCType fromType,UnitXCType toType, Map<String,UnitXConverterParameterValue> parameters) {
+		Validate.notNull(valueConvert2,"Can't convert null to number");
+		Validate.notNull(fromType,"Can't convert from null unit type");
+		Validate.notNull(toType,"Can't convert to null unit type");
+		
+		
+		if (fromType.getAliasOfType() != null) {
+			fromType = Validate.notNull(manager.getUnitType(fromType.getAliasOfType()),"Coultn't resolve alias id: "+fromType.getAliasOfType()+" for: "+fromType.getId());
+		}
+		if (toType.getAliasOfType() != null) {
+			toType = Validate.notNull(manager.getUnitType(toType.getAliasOfType()),"Coultn't resolve alias id: "+toType.getAliasOfType()+" for: "+toType.getId());
+		}
+		
 		double valueConvert = valueConvert2.doubleValue();
 		long startTime = System.currentTimeMillis();
 		MathContext mathContext = MathContext.DECIMAL128;
@@ -178,7 +190,7 @@ public final class UnitXConverterEngine {
 			step.runStep(this);
 			long convertTime = System.currentTimeMillis()-startTime;
 			
-			System.out.println("runStep: "+step+" res: "+step.getStepReasons());
+//			System.out.println("runStep: "+step+" res: "+step.getStepReasons());
 			
 			UnitXConverterResultStep resultStep = new UnitXConverterResultStep();
 			resultStep.setStartValue(valueOld);
diff --git a/ff-unitxc-converter/src/main/java/net/forwardfire/unitxc/model/step/value/UnitXConverterStepValueNamedParameter.java b/ff-unitxc-converter/src/main/java/net/forwardfire/unitxc/model/step/value/UnitXConverterStepValueNamedParameter.java
index 423cf4a..6c52411 100644
--- a/ff-unitxc-converter/src/main/java/net/forwardfire/unitxc/model/step/value/UnitXConverterStepValueNamedParameter.java
+++ b/ff-unitxc-converter/src/main/java/net/forwardfire/unitxc/model/step/value/UnitXConverterStepValueNamedParameter.java
@@ -52,13 +52,6 @@ public class UnitXConverterStepValueNamedParameter implements UnitXConverterStep
 		return ctx.getNamedParameter(parameterName).valueRead(ctx);
 	}
 	
-	@Override
-	public UnitXConverterStepValueRead clone() {
-		UnitXConverterStepValueNamedParameter clone = new UnitXConverterStepValueNamedParameter();
-		clone.setParameterName(getParameterName());
-		return clone;
-	}
-	
 	/**
 	 * @return the parameterName
 	 */
diff --git a/ff-unitxc-converter/src/main/java/net/forwardfire/unitxc/model/step/value/UnitXConverterStepValueNamedVariable.java b/ff-unitxc-converter/src/main/java/net/forwardfire/unitxc/model/step/value/UnitXConverterStepValueNamedVariable.java
index 91e030f..9c7bdd4 100644
--- a/ff-unitxc-converter/src/main/java/net/forwardfire/unitxc/model/step/value/UnitXConverterStepValueNamedVariable.java
+++ b/ff-unitxc-converter/src/main/java/net/forwardfire/unitxc/model/step/value/UnitXConverterStepValueNamedVariable.java
@@ -58,14 +58,6 @@ public class UnitXConverterStepValueNamedVariable implements UnitXConverterStepV
 	public void valueWrite(UnitXConverterStepContext ctx,Object value) {
 		ctx.getNamedVariable(variableName).valueWrite(ctx,value);
 	}
-
-	@Override
-	public UnitXConverterStepValueReadWrite clone() {
-		UnitXConverterStepValueNamedVariable clone = new UnitXConverterStepValueNamedVariable();
-		clone.setValueType(getValueType());
-		clone.setVariableName(getVariableName());
-		return clone;
-	}
 	
 	/**
 	 * @return the variableName
diff --git a/ff-unitxc-converter/src/main/java/net/forwardfire/unitxc/model/step/value/UnitXConverterStepValueRead.java b/ff-unitxc-converter/src/main/java/net/forwardfire/unitxc/model/step/value/UnitXConverterStepValueRead.java
index 9b7ceda..5e9964a 100644
--- a/ff-unitxc-converter/src/main/java/net/forwardfire/unitxc/model/step/value/UnitXConverterStepValueRead.java
+++ b/ff-unitxc-converter/src/main/java/net/forwardfire/unitxc/model/step/value/UnitXConverterStepValueRead.java
@@ -31,9 +31,7 @@ import net.forwardfire.unitxc.model.step.UnitXConverterStepContext;
  * @author Willem Cazander
  * @version 1.0 Apr 1, 2016
  */
-public interface UnitXConverterStepValueRead extends Cloneable {
+public interface UnitXConverterStepValueRead {
 	
 	Object valueRead(UnitXConverterStepContext ctx);
-	
-	UnitXConverterStepValueRead clone();
 }
diff --git a/ff-unitxc-converter/src/main/java/net/forwardfire/unitxc/model/step/value/UnitXConverterStepValueReadWrite.java b/ff-unitxc-converter/src/main/java/net/forwardfire/unitxc/model/step/value/UnitXConverterStepValueReadWrite.java
index 31270a6..84edff3 100644
--- a/ff-unitxc-converter/src/main/java/net/forwardfire/unitxc/model/step/value/UnitXConverterStepValueReadWrite.java
+++ b/ff-unitxc-converter/src/main/java/net/forwardfire/unitxc/model/step/value/UnitXConverterStepValueReadWrite.java
@@ -34,6 +34,4 @@ import net.forwardfire.unitxc.model.step.UnitXConverterStepContext;
 public interface UnitXConverterStepValueReadWrite extends UnitXConverterStepValueRead {
 
 	void valueWrite(UnitXConverterStepContext ctx,Object value);
-	
-	UnitXConverterStepValueReadWrite clone();
 }
diff --git a/ff-unitxc-converter/src/main/java/net/forwardfire/unitxc/model/step/value/UnitXConverterStepValueReferenceDouble.java b/ff-unitxc-converter/src/main/java/net/forwardfire/unitxc/model/step/value/UnitXConverterStepValueReferenceDouble.java
index a529dfb..1aebf49 100644
--- a/ff-unitxc-converter/src/main/java/net/forwardfire/unitxc/model/step/value/UnitXConverterStepValueReferenceDouble.java
+++ b/ff-unitxc-converter/src/main/java/net/forwardfire/unitxc/model/step/value/UnitXConverterStepValueReferenceDouble.java
@@ -57,11 +57,6 @@ public class UnitXConverterStepValueReferenceDouble implements UnitXConverterSte
 		this.value = Double.class.cast(value);
 	}
 	
-	@Override
-	public UnitXConverterStepValueReadWrite clone() {
-		return new UnitXConverterStepValueReferenceDouble(getValue());
-	}
-	
 	/**
 	 * @return the value
 	 */
diff --git a/ff-unitxc-converter/src/main/java/net/forwardfire/unitxc/model/step/value/UnitXConverterStepValueReferenceDoubleFraction.java b/ff-unitxc-converter/src/main/java/net/forwardfire/unitxc/model/step/value/UnitXConverterStepValueReferenceDoubleFraction.java
index 29bd1d0..0988454 100644
--- a/ff-unitxc-converter/src/main/java/net/forwardfire/unitxc/model/step/value/UnitXConverterStepValueReferenceDoubleFraction.java
+++ b/ff-unitxc-converter/src/main/java/net/forwardfire/unitxc/model/step/value/UnitXConverterStepValueReferenceDoubleFraction.java
@@ -57,11 +57,6 @@ public class UnitXConverterStepValueReferenceDoubleFraction implements UnitXConv
 		return (Double)(((Integer)numerator).doubleValue()/((Integer)denominator).doubleValue());  // FIXME
 	}
 	
-	@Override
-	public UnitXConverterStepValueRead clone() {
-		return new UnitXConverterStepValueReferenceDoubleFraction(getNumerator(),getDenominator());
-	}
-	
 	/**
 	 * @return the numerator
 	 */
diff --git a/ff-unitxc-converter/src/main/java/net/forwardfire/unitxc/model/step/value/UnitXConverterStepValueReferenceInteger.java b/ff-unitxc-converter/src/main/java/net/forwardfire/unitxc/model/step/value/UnitXConverterStepValueReferenceInteger.java
index 52f1c8c..e4631da 100644
--- a/ff-unitxc-converter/src/main/java/net/forwardfire/unitxc/model/step/value/UnitXConverterStepValueReferenceInteger.java
+++ b/ff-unitxc-converter/src/main/java/net/forwardfire/unitxc/model/step/value/UnitXConverterStepValueReferenceInteger.java
@@ -57,11 +57,6 @@ public class UnitXConverterStepValueReferenceInteger implements UnitXConverterSt
 		this.value = Integer.class.cast(value);
 	}
 	
-	@Override
-	public UnitXConverterStepValueReadWrite clone() {
-		return new UnitXConverterStepValueReferenceInteger(getValue());
-	}
-	
 	/**
 	 * @return the value
 	 */
diff --git a/ff-unitxc-converter/src/main/java/net/forwardfire/unitxc/model/step/value/UnitXConverterStepValueReferenceString.java b/ff-unitxc-converter/src/main/java/net/forwardfire/unitxc/model/step/value/UnitXConverterStepValueReferenceString.java
index d3115a7..a1a6d81 100644
--- a/ff-unitxc-converter/src/main/java/net/forwardfire/unitxc/model/step/value/UnitXConverterStepValueReferenceString.java
+++ b/ff-unitxc-converter/src/main/java/net/forwardfire/unitxc/model/step/value/UnitXConverterStepValueReferenceString.java
@@ -57,11 +57,6 @@ public class UnitXConverterStepValueReferenceString implements UnitXConverterSte
 		this.value = String.class.cast(value);
 	}
 	
-	@Override
-	public UnitXConverterStepValueReadWrite clone() {
-		return new UnitXConverterStepValueReferenceString(getValue());
-	}
-	
 	/**
 	 * @return the value
 	 */
diff --git a/ff-unitxc-converter/src/test/java/net/forwardfire/unitxc/UnitXCManagerTest.java b/ff-unitxc-converter/src/test/java/net/forwardfire/unitxc/UnitXCManagerTest.java
index 387a751..32e062a 100644
--- a/ff-unitxc-converter/src/test/java/net/forwardfire/unitxc/UnitXCManagerTest.java
+++ b/ff-unitxc-converter/src/test/java/net/forwardfire/unitxc/UnitXCManagerTest.java
@@ -1,6 +1,7 @@
 package net.forwardfire.unitxc;
 
 import static org.junit.Assert.assertNotNull;
+import static org.junit.Assert.assertNull;
 import static org.junit.Assert.assertTrue;
 import static org.junit.Assert.assertFalse;
 
@@ -27,9 +28,9 @@ public class UnitXCManagerTest {
 		assertNotNull(test.getUnitType(null));
 	}
 	
-	@Test(expected=NullPointerException.class)
+	@Test
 	public void testGetUnitTypeInvalid() {
-		assertNotNull(test.getUnitType(getClass().getName()));
+		assertNull(test.getUnitType(getClass().getName()));
 	}
 	
 	@Test