diff --git a/com.ibm.wala.core/src/com/ibm/wala/analysis/typeInference/TypeVariable.java b/com.ibm.wala.core/src/com/ibm/wala/analysis/typeInference/TypeVariable.java
index fc6ba0553..a2b24ebc7 100644
--- a/com.ibm.wala.core/src/com/ibm/wala/analysis/typeInference/TypeVariable.java
+++ b/com.ibm.wala.core/src/com/ibm/wala/analysis/typeInference/TypeVariable.java
@@ -14,7 +14,7 @@ import com.ibm.wala.fixedpoint.impl.AbstractVariable;
 /**
  * A type variable in the dataflow system.
  */
-public class TypeVariable extends AbstractVariable {
+public class TypeVariable extends AbstractVariable<TypeVariable> {
 
   TypeAbstraction type;
 
diff --git a/com.ibm.wala.core/src/com/ibm/wala/fixedpoint/impl/AbstractVariable.java b/com.ibm.wala.core/src/com/ibm/wala/fixedpoint/impl/AbstractVariable.java
index 87612c47b..2e3bde1c2 100644
--- a/com.ibm.wala.core/src/com/ibm/wala/fixedpoint/impl/AbstractVariable.java
+++ b/com.ibm.wala.core/src/com/ibm/wala/fixedpoint/impl/AbstractVariable.java
@@ -18,7 +18,7 @@ import com.ibm.wala.util.graph.impl.NodeWithNumber;
  * 
  * @author Stephen Fink
  */
-public abstract class AbstractVariable extends NodeWithNumber implements IVariable {
+public abstract class AbstractVariable<T extends AbstractVariable> extends NodeWithNumber implements IVariable<T> {
 
   private int orderNumber;
 
diff --git a/com.ibm.wala.core/src/com/ibm/wala/fixpoint/BitVectorVariable.java b/com.ibm.wala.core/src/com/ibm/wala/fixpoint/BitVectorVariable.java
index f98421c6d..ec20d56ed 100644
--- a/com.ibm.wala.core/src/com/ibm/wala/fixpoint/BitVectorVariable.java
+++ b/com.ibm.wala.core/src/com/ibm/wala/fixpoint/BitVectorVariable.java
@@ -23,7 +23,7 @@ import com.ibm.wala.util.intset.MutableSharedBitVectorIntSet;
  * 
  * @author sfink
  */
-public class BitVectorVariable extends AbstractVariable {
+public class BitVectorVariable extends AbstractVariable<BitVectorVariable> {
 
   private MutableSharedBitVectorIntSet V;
   private final int hash;
diff --git a/com.ibm.wala.core/src/com/ibm/wala/fixpoint/BooleanVariable.java b/com.ibm.wala.core/src/com/ibm/wala/fixpoint/BooleanVariable.java
index 61b3dc35a..7da3fa648 100644
--- a/com.ibm.wala.core/src/com/ibm/wala/fixpoint/BooleanVariable.java
+++ b/com.ibm.wala.core/src/com/ibm/wala/fixpoint/BooleanVariable.java
@@ -18,7 +18,7 @@ import com.ibm.wala.fixedpoint.impl.AbstractVariable;
  * 
  * @author sfink
  */
-public class BooleanVariable extends AbstractVariable {
+public class BooleanVariable extends AbstractVariable<BooleanVariable> {
 
   private boolean B;
 
diff --git a/com.ibm.wala.core/src/com/ibm/wala/fixpoint/IVariable.java b/com.ibm.wala.core/src/com/ibm/wala/fixpoint/IVariable.java
index 1b2612fb7..782078b96 100644
--- a/com.ibm.wala.core/src/com/ibm/wala/fixpoint/IVariable.java
+++ b/com.ibm.wala.core/src/com/ibm/wala/fixpoint/IVariable.java
@@ -19,7 +19,7 @@ import com.ibm.wala.util.graph.INodeWithNumber;
  * 
  * @author Stephen Fink
  */
-public interface IVariable extends INodeWithNumber {
+public interface IVariable<T extends IVariable> extends INodeWithNumber {
 
   
   /**
@@ -44,4 +44,11 @@ public interface IVariable extends INodeWithNumber {
    */
   public abstract void setOrderNumber(int i);
 
+  /**
+    * Set this variable to have the same state as another one
+    * 
+    * @param v
+    */
+  public void copyState(T v);
+
 }
\ No newline at end of file
diff --git a/com.ibm.wala.core/src/com/ibm/wala/fixpoint/IntSetVariable.java b/com.ibm.wala.core/src/com/ibm/wala/fixpoint/IntSetVariable.java
index 656bb5a9d..a52a9a64d 100644
--- a/com.ibm.wala.core/src/com/ibm/wala/fixpoint/IntSetVariable.java
+++ b/com.ibm.wala.core/src/com/ibm/wala/fixpoint/IntSetVariable.java
@@ -24,11 +24,11 @@ import com.ibm.wala.util.intset.MutableIntSet;
  * 
  * @author sfink
  */
-public abstract class IntSetVariable extends AbstractVariable {
+public abstract class IntSetVariable<T extends IntSetVariable> extends AbstractVariable<T> {
 
   private MutableIntSet V;
 
-  public void copyState(IntSetVariable other) {
+  public void copyState(T other) {
     if (V == null) {
       if (other.V == null) {
         return;
@@ -64,7 +64,7 @@ public abstract class IntSetVariable extends AbstractVariable {
    * 
    * @return true iff the contents of this variable changes.
    */
-  public boolean addAll(IntSetVariable other) {
+  public boolean addAll(T other) {
     if (V == null) {
       copyState(other);
       return (V != null);
@@ -157,7 +157,7 @@ public abstract class IntSetVariable extends AbstractVariable {
     return V.containsAny(instances);
   }
 
-  public boolean addAllInIntersection(IntSetVariable other, IntSet filter) {
+  public boolean addAllInIntersection(T other, IntSet filter) {
     if (V == null) {
       copyState(other);
       if (V != null) {
diff --git a/com.ibm.wala.core/src/com/ibm/wala/ipa/callgraph/propagation/PointsToSetVariable.java b/com.ibm.wala.core/src/com/ibm/wala/ipa/callgraph/propagation/PointsToSetVariable.java
index bbb733b28..82b1a45ed 100644
--- a/com.ibm.wala.core/src/com/ibm/wala/ipa/callgraph/propagation/PointsToSetVariable.java
+++ b/com.ibm.wala.core/src/com/ibm/wala/ipa/callgraph/propagation/PointsToSetVariable.java
@@ -17,7 +17,7 @@ import com.ibm.wala.util.debug.Assertions;
  * @author sfink
  * 
  */
-public class PointsToSetVariable extends IntSetVariable {
+public class PointsToSetVariable extends IntSetVariable<PointsToSetVariable> {
   private PointerKey pointerKey;
 
   public PointsToSetVariable(PointerKey key) {