diff --git a/prism/src/explicit/StateValues.java b/prism/src/explicit/StateValues.java
index 916094d7..7fe52326 100644
--- a/prism/src/explicit/StateValues.java
+++ b/prism/src/explicit/StateValues.java
@@ -131,18 +131,18 @@ public class StateValues
 		// Create/initialise array of appropriate type
 		if (type instanceof TypeInt) {
 			valuesI = new int[size];
-			Integer objI = (Integer) type.castValueTo(init);
+			Integer objI = ((TypeInt) type).castValueTo(init);
 			int initI = objI.intValue();
 			for (i = 0; i < size; i++)
 				valuesI[i] = initI;
 		} else if (type instanceof TypeDouble) {
 			valuesD = new double[size];
-			Double objD = (Double) type.castValueTo(init);
+			Double objD = ((TypeDouble) type).castValueTo(init);
 			double initD = objD.doubleValue();
 			for (i = 0; i < size; i++)
 				valuesD[i] = initD;
 		} else if (type instanceof TypeBool) {
-			Boolean objB = (Boolean) type.castValueTo(init);
+			Boolean objB = ((TypeBool) type).castValueTo(init);
 			boolean initB = objB.booleanValue();
 			if (initB) {
 				valuesB = new BitSet(size);
diff --git a/prism/src/parser/type/TypeBool.java b/prism/src/parser/type/TypeBool.java
index 6496dffd..1b6aa4fd 100644
--- a/prism/src/parser/type/TypeBool.java
+++ b/prism/src/parser/type/TypeBool.java
@@ -70,10 +70,10 @@ public class TypeBool extends Type
 	}
 	
 	@Override
-	public Object castValueTo(Object value) throws PrismLangException
+	public Boolean castValueTo(Object value) throws PrismLangException
 	{
 		if (value instanceof Boolean)
-			return value;
+			return (Boolean) value;
 		else
 			throw new PrismLangException("Can't convert " + value.getClass() + " to type " + getTypeString());
 	}
diff --git a/prism/src/parser/type/TypeClock.java b/prism/src/parser/type/TypeClock.java
index 1285b1d4..41667ec3 100644
--- a/prism/src/parser/type/TypeClock.java
+++ b/prism/src/parser/type/TypeClock.java
@@ -70,10 +70,10 @@ public class TypeClock extends Type
 	}
 	
 	@Override
-	public Object castValueTo(Object value) throws PrismLangException
+	public Double castValueTo(Object value) throws PrismLangException
 	{
 		if (value instanceof Double)
-			return value;
+			return (Double) value;
 		if (value instanceof Integer)
 			return new Double(((Double) value).doubleValue());
 		else
diff --git a/prism/src/parser/type/TypeDouble.java b/prism/src/parser/type/TypeDouble.java
index 7cc03d73..7c9bfad0 100644
--- a/prism/src/parser/type/TypeDouble.java
+++ b/prism/src/parser/type/TypeDouble.java
@@ -70,10 +70,10 @@ public class TypeDouble extends Type
 	}
 	
 	@Override
-	public Object castValueTo(Object value) throws PrismLangException
+	public Double castValueTo(Object value) throws PrismLangException
 	{
 		if (value instanceof Double)
-			return value;
+			return (Double) value;
 		if (value instanceof Integer)
 			return new Double(((Double) value).doubleValue());
 		else
diff --git a/prism/src/parser/type/TypeInt.java b/prism/src/parser/type/TypeInt.java
index a33f322a..14b47ea7 100644
--- a/prism/src/parser/type/TypeInt.java
+++ b/prism/src/parser/type/TypeInt.java
@@ -70,10 +70,10 @@ public class TypeInt extends Type
 	}
 	
 	@Override
-	public Object castValueTo(Object value) throws PrismLangException
+	public Integer castValueTo(Object value) throws PrismLangException
 	{
 		if (value instanceof Integer)
-			return value;
+			return (Integer) value;
 		else
 			throw new PrismLangException("Can't convert " + value.getClass() + " to type " + getTypeString());
 	}