diff --git a/classpath/java/io/ObjectInputStream.java b/classpath/java/io/ObjectInputStream.java
index 531058b943..15394c5d0b 100644
--- a/classpath/java/io/ObjectInputStream.java
+++ b/classpath/java/io/ObjectInputStream.java
@@ -204,7 +204,11 @@ public class ObjectInputStream extends InputStream {
     for (Field f: c.getFields()) {
       int modifiers = f.getModifiers();
       if ((modifiers & (Modifier.TRANSIENT | Modifier.STATIC)) == 0) {
-        f.set(o, deserialize(map));
+        try {
+          f.set(o, deserialize(map));
+        } catch (Exception e) {
+          throw new RuntimeException(e);
+        }
       }
     }
 
diff --git a/classpath/java/io/ObjectOutputStream.java b/classpath/java/io/ObjectOutputStream.java
index 25b20adeae..330a3e0c98 100644
--- a/classpath/java/io/ObjectOutputStream.java
+++ b/classpath/java/io/ObjectOutputStream.java
@@ -155,7 +155,14 @@ public class ObjectOutputStream extends OutputStream {
       int modifiers = f.getModifiers();
       if ((modifiers & (Modifier.TRANSIENT | Modifier.STATIC)) == 0) {
         out.print(" ");
-        Object v = f.get(o);
+        Object v;
+
+        try {
+          v = f.get(o);
+        } catch (Exception e) {
+          throw new RuntimeException(e);
+        }
+
         Class t = f.getType();
         if (t.equals(boolean.class)) {
           writeBoolean((Boolean) v);
diff --git a/classpath/java/util/HashMap.java b/classpath/java/util/HashMap.java
index d5f860ad93..abb559279f 100644
--- a/classpath/java/util/HashMap.java
+++ b/classpath/java/util/HashMap.java
@@ -53,8 +53,8 @@ public class HashMap<K, V> implements Map<K, V> {
           for (Cell<K, V> c = array[i]; c != null; c = next) {
             next = c.next();
             int index = c.hashCode() & (capacity - 1);
-            c.setNext(array[index]);
-            array[index] = c;
+            c.setNext(newArray[index]);
+            newArray[index] = c;
           }
         }
       }
diff --git a/classpath/java/util/LinkedList.java b/classpath/java/util/LinkedList.java
index f521940778..5deae40931 100644
--- a/classpath/java/util/LinkedList.java
+++ b/classpath/java/util/LinkedList.java
@@ -127,8 +127,7 @@ public class LinkedList<T> implements List<T> {
   public T removeFirst() {
     if (front != null) {
       T v = front.value;
-      front = front.next;
-      if (front != null) front.prev = null;
+      remove(front);
       return v;
     } else {
       throw new NoSuchElementException();
@@ -138,8 +137,7 @@ public class LinkedList<T> implements List<T> {
   public T removeLast() {
     if (rear != null) {
       T v = rear.value;
-      rear = rear.prev;
-      if (rear != null) rear.next = null;
+      remove(rear);
       return v;
     } else {
       throw new NoSuchElementException();
diff --git a/src/builtin.cpp b/src/builtin.cpp
index 1d63e19240..1780014946 100644
--- a/src/builtin.cpp
+++ b/src/builtin.cpp
@@ -627,16 +627,16 @@ Throwable_trace(Thread* t, jclass, jint skipCount)
     frame = frameNext(t, frame);
   }
   
-  if (methodClass(t, frameMethod(t, frame))
-      == arrayBody(t, t->vm->types, Machine::ThrowableType))
+  // skip Throwable constructors
+  while (frame >= 0
+         and isAssignableFrom
+         (t, arrayBody(t, t->vm->types, Machine::ThrowableType),
+          methodClass(t, frameMethod(t, frame)))
+         and strcmp(reinterpret_cast<const int8_t*>("<init>"),
+                    &byteArrayBody(t, methodName(t, frameMethod(t, frame)), 0))
+         == 0)
   {
-    // skip Throwable constructors
-    while (strcmp(reinterpret_cast<const int8_t*>("<init>"),
-                  &byteArrayBody(t, methodName(t, frameMethod(t, frame)), 0))
-           == 0)
-    {
-      frame = frameNext(t, frame);
-    }
+    frame = frameNext(t, frame);
   }
 
   return pushReference(t, makeTrace(t, frame));
diff --git a/src/machine.cpp b/src/machine.cpp
index 849ea0c418..c933a790bc 100644
--- a/src/machine.cpp
+++ b/src/machine.cpp
@@ -271,8 +271,7 @@ postVisit(Thread* t, Heap::Visitor* v)
     if (m->heap->status(*p) == Heap::Unreachable) {
       // reference is unreachable
       referenceUnreachable(t, p, v);
-    } else if (jreferenceTarget(t, *p) == 0
-               or m->heap->status(jreferenceTarget(t, *p))
+    } else if (m->heap->status(jreferenceTarget(t, *p))
                == Heap::Unreachable)
     {
       // target is unreachable
@@ -318,8 +317,7 @@ postVisit(Thread* t, Heap::Visitor* v)
       if (m->heap->status(*p) == Heap::Unreachable) {
         // reference is unreachable
         referenceUnreachable(t, p, v);
-      } else if (jreferenceTarget(t, *p) == 0
-                 or m->heap->status(jreferenceTarget(t, *p))
+      } else if (m->heap->status(jreferenceTarget(t, *p))
                  == Heap::Unreachable)
       {
         // target is unreachable