diff --git a/hyracks-dataflow-common/src/main/java/edu/uci/ics/hyracks/dataflow/common/comm/io/FrameTupleAppender.java b/hyracks-dataflow-common/src/main/java/edu/uci/ics/hyracks/dataflow/common/comm/io/FrameTupleAppender.java
index 460d049..bd5a907 100644
--- a/hyracks-dataflow-common/src/main/java/edu/uci/ics/hyracks/dataflow/common/comm/io/FrameTupleAppender.java
+++ b/hyracks-dataflow-common/src/main/java/edu/uci/ics/hyracks/dataflow/common/comm/io/FrameTupleAppender.java
@@ -16,6 +16,7 @@
 
 import java.nio.ByteBuffer;
 
+import edu.uci.ics.hyracks.api.comm.IFrameTupleAccessor;
 import edu.uci.ics.hyracks.api.context.IHyracksContext;
 
 public class FrameTupleAppender {
@@ -59,7 +60,7 @@
         return false;
     }
 
-    public boolean append(FrameTupleAccessor tupleAccessor, int tStartOffset, int tEndOffset) {
+    public boolean append(IFrameTupleAccessor tupleAccessor, int tStartOffset, int tEndOffset) {
         int length = tEndOffset - tStartOffset;
         if (tupleDataEndOffset + length + 4 + (tupleCount + 1) * 4 <= ctx.getFrameSize()) {
             ByteBuffer src = tupleAccessor.getBuffer();
@@ -73,13 +74,13 @@
         return false;
     }
 
-    public boolean append(FrameTupleAccessor tupleAccessor, int tIndex) {
+    public boolean append(IFrameTupleAccessor tupleAccessor, int tIndex) {
         int tStartOffset = tupleAccessor.getTupleStartOffset(tIndex);
         int tEndOffset = tupleAccessor.getTupleEndOffset(tIndex);
         return append(tupleAccessor, tStartOffset, tEndOffset);
     }
 
-    public boolean appendConcat(FrameTupleAccessor accessor0, int tIndex0, FrameTupleAccessor accessor1, int tIndex1) {
+    public boolean appendConcat(IFrameTupleAccessor accessor0, int tIndex0, IFrameTupleAccessor accessor1, int tIndex1) {
         int startOffset0 = accessor0.getTupleStartOffset(tIndex0);
         int endOffset0 = accessor0.getTupleEndOffset(tIndex0);
         int length0 = endOffset0 - startOffset0;
@@ -117,7 +118,7 @@
         return false;
     }
 
-    public boolean appendProjection(FrameTupleAccessor accessor, int tIndex, int[] fields) {
+    public boolean appendProjection(IFrameTupleAccessor accessor, int tIndex, int[] fields) {
         int fTargetSlotsLength = fields.length * 2;
         int length = fTargetSlotsLength;
         for (int i = 0; i < fields.length; ++i) {
diff --git a/hyracks-dataflow-hadoop/src/main/java/edu/uci/ics/hyracks/dataflow/hadoop/data/WritableComparingComparatorFactory.java b/hyracks-dataflow-hadoop/src/main/java/edu/uci/ics/hyracks/dataflow/hadoop/data/WritableComparingComparatorFactory.java
index c78648f..cec29d5 100644
--- a/hyracks-dataflow-hadoop/src/main/java/edu/uci/ics/hyracks/dataflow/hadoop/data/WritableComparingComparatorFactory.java
+++ b/hyracks-dataflow-hadoop/src/main/java/edu/uci/ics/hyracks/dataflow/hadoop/data/WritableComparingComparatorFactory.java
@@ -16,16 +16,15 @@
 
 import org.apache.hadoop.io.RawComparator;
 import org.apache.hadoop.io.WritableComparable;
-import org.apache.hadoop.io.WritableComparator;
 
 import edu.uci.ics.hyracks.api.dataflow.value.IComparator;
 import edu.uci.ics.hyracks.api.dataflow.value.IComparatorFactory;
 import edu.uci.ics.hyracks.dataflow.common.util.ReflectionUtils;
 
 public class WritableComparingComparatorFactory<T> implements IComparatorFactory<WritableComparable<T>> {
-    private Class<? extends RawComparator> klass;
+    private Class<? extends RawComparator<? super WritableComparable<T>>> klass;
 
-    public WritableComparingComparatorFactory(Class<? extends WritableComparator> klass) {
+    public WritableComparingComparatorFactory(Class<? extends RawComparator<? super WritableComparable<T>>> klass) {
         this.klass = klass;
     }
 
@@ -33,7 +32,7 @@
 
     @Override
     public IComparator<WritableComparable<T>> createComparator() {
-        final RawComparator<WritableComparable<T>> instance = ReflectionUtils.createInstance(klass);
+        final RawComparator<? super WritableComparable<T>> instance = ReflectionUtils.createInstance(klass);
         return new IComparator<WritableComparable<T>>() {
             @Override
             public int compare(WritableComparable<T> o1, WritableComparable<T> o2) {