diff --git a/src/main/scala/scala/async/internal/LiveVariables.scala b/src/main/scala/scala/async/internal/LiveVariables.scala
index 71fd0aca..2f7ecc29 100644
--- a/src/main/scala/scala/async/internal/LiveVariables.scala
+++ b/src/main/scala/scala/async/internal/LiveVariables.scala
@@ -143,7 +143,7 @@ trait LiveVariables {
      * A state `i` is contained in the list that is the value to which
      * key `j` maps iff control can flow from state `j` to state `i`.
      */
-    val cfg: Map[Int, Array[Int]] = {
+    val cfg: IntMap[Array[Int]] = {
       var res = IntMap.empty[Array[Int]]
 
       for (as <- asyncStates) res = res.updated(as.state, as.nextStates)
@@ -158,8 +158,9 @@ trait LiveVariables {
       def isPred0(state1: Int, state2: Int): Boolean = 
         if(state1 == state2) false
         else if (seen.contains(state1)) false  // breaks cycles in the CFG
-        else cfg get state1 match {
-          case Some(nextStates) =>
+        else cfg getOrElse(state1, null) match {
+          case null => false
+          case nextStates =>
             seen += state1
             var i = 0
             while (i < nextStates.length) {
@@ -167,8 +168,6 @@ trait LiveVariables {
               i += 1
             }
             false
-          case None =>
-            false
         }
 
       isPred0(state1, state2)
diff --git a/src/main/scala/scala/async/internal/StateSet.scala b/src/main/scala/scala/async/internal/StateSet.scala
index a13e9f16..7b7c8124 100644
--- a/src/main/scala/scala/async/internal/StateSet.scala
+++ b/src/main/scala/scala/async/internal/StateSet.scala
@@ -19,10 +19,13 @@ import scala.collection.JavaConverters.{asScalaIteratorConverter, iterableAsScal
 
 // Set for StateIds, which are either small positive integers or -symbolID.
 final class StateSet {
-  private var bitSet = new java.util.BitSet()
-  private var caseSet = new util.HashSet[Integer]()
-  def +=(stateId: Int): Unit = if (stateId > 0) bitSet.set(stateId) else caseSet.add(stateId)
-  def contains(stateId: Int): Boolean = if (stateId > 0 && stateId < 1024) bitSet.get(stateId) else caseSet.contains(stateId)
+  private val bitSet = new java.util.BitSet()
+  private val caseSet = new util.HashSet[Integer]()
+  def +=(stateId: Int): Unit = if (storeInBitSet(stateId)) bitSet.set(stateId) else caseSet.add(stateId)
+  def contains(stateId: Int): Boolean = if (storeInBitSet(stateId)) bitSet.get(stateId) else caseSet.contains(stateId)
+  private def storeInBitSet(stateId: Int) = {
+    stateId > 0 && stateId < 1024
+  }
   def iterator: Iterator[Integer] = {
     bitSet.stream().iterator().asScala ++ caseSet.asScala.iterator
   }