diff --git a/src/main/java/com/android/tools/r8/D8.java b/src/main/java/com/android/tools/r8/D8.java
index a2b0fd9..33e383c 100644
--- a/src/main/java/com/android/tools/r8/D8.java
+++ b/src/main/java/com/android/tools/r8/D8.java
@@ -55,7 +55,7 @@
  */
 public final class D8 {
 
-  private static final String VERSION = "v0.1.4";
+  private static final String VERSION = "v0.1.5";
   private static final int STATUS_ERROR = 1;
 
   private D8() {}
diff --git a/src/main/java/com/android/tools/r8/R8.java b/src/main/java/com/android/tools/r8/R8.java
index c05750a..45b43db 100644
--- a/src/main/java/com/android/tools/r8/R8.java
+++ b/src/main/java/com/android/tools/r8/R8.java
@@ -71,7 +71,7 @@
 
 public class R8 {
 
-  private static final String VERSION = "v0.1.4";
+  private static final String VERSION = "v0.1.5";
   private final Timing timing = new Timing("R8");
   private final InternalOptions options;
 
diff --git a/src/main/java/com/android/tools/r8/ir/code/ConstNumber.java b/src/main/java/com/android/tools/r8/ir/code/ConstNumber.java
index 1880668..708e5a4 100644
--- a/src/main/java/com/android/tools/r8/ir/code/ConstNumber.java
+++ b/src/main/java/com/android/tools/r8/ir/code/ConstNumber.java
@@ -26,7 +26,6 @@
     // are all for fixed register values. All other values that are used as the destination for
     // const number instructions should be marked as constants.
     assert dest.isFixedRegisterValue() || dest.definition.isConstNumber();
-    assert type != ConstType.OBJECT;
     this.type = type;
     this.value = value;
   }
@@ -53,7 +52,7 @@
   }
 
   public int getIntValue() {
-    assert type == ConstType.INT || type == ConstType.INT_OR_FLOAT;
+    assert type == ConstType.INT || type == ConstType.INT_OR_FLOAT || type == ConstType.OBJECT;
     return (int) value;
   }
 
@@ -96,7 +95,7 @@
     }
 
     int register = builder.allocatedRegister(dest(), getNumber());
-    if (MoveType.fromConstType(type) == MoveType.SINGLE) {
+    if (MoveType.fromConstType(type) == MoveType.SINGLE || type == ConstType.OBJECT) {
       assert NumberUtils.is32Bit(value);
       if ((register & 0xf) == register && NumberUtils.is4Bit(value)) {
         builder.add(this, new Const4(register, (int) value));
diff --git a/src/main/java/com/android/tools/r8/ir/conversion/IRBuilder.java b/src/main/java/com/android/tools/r8/ir/conversion/IRBuilder.java
index 976020c2..aa86057 100644
--- a/src/main/java/com/android/tools/r8/ir/conversion/IRBuilder.java
+++ b/src/main/java/com/android/tools/r8/ir/conversion/IRBuilder.java
@@ -716,7 +716,7 @@
   }
 
   public void addNullConst(int dest, long value) {
-    canonicalizeAndAddConst(ConstType.INT, dest, value, nullConstants);
+    canonicalizeAndAddConst(ConstType.OBJECT, dest, value, nullConstants);
   }
 
   public void addConstClass(int dest, DexType type) {
diff --git a/src/main/java/com/android/tools/r8/ir/optimize/CodeRewriter.java b/src/main/java/com/android/tools/r8/ir/optimize/CodeRewriter.java
index 815efe4..0c75ef3 100644
--- a/src/main/java/com/android/tools/r8/ir/optimize/CodeRewriter.java
+++ b/src/main/java/com/android/tools/r8/ir/optimize/CodeRewriter.java
@@ -78,6 +78,7 @@
 import java.util.Comparator;
 import java.util.HashMap;
 import java.util.HashSet;
+import java.util.IdentityHashMap;
 import java.util.Iterator;
 import java.util.LinkedList;
 import java.util.List;
@@ -845,7 +846,7 @@
         if (current.isInvoke() && current.asInvoke().requiredArgumentRegisters() > 5) {
           Invoke invoke = current.asInvoke();
           it.previous();
-          Map<ConstNumber, ConstNumber> oldToNew = new HashMap<>();
+          Map<ConstNumber, ConstNumber> oldToNew = new IdentityHashMap<>();
           for (int i = 0; i < invoke.inValues().size(); i++) {
             Value value = invoke.inValues().get(i);
             if (value.isConstNumber() && value.numberOfUsers() > 1) {