diff --git a/teavm-core/src/main/java/org/teavm/javascript/Optimizer.java b/teavm-core/src/main/java/org/teavm/javascript/Optimizer.java
index c57a126f7..9ffdd31de 100644
--- a/teavm-core/src/main/java/org/teavm/javascript/Optimizer.java
+++ b/teavm-core/src/main/java/org/teavm/javascript/Optimizer.java
@@ -15,11 +15,15 @@
  */
 package org.teavm.javascript;
 
+import java.util.*;
+import org.teavm.common.Graph;
 import org.teavm.javascript.ast.AsyncMethodNode;
 import org.teavm.javascript.ast.AsyncMethodPart;
 import org.teavm.javascript.ast.RegularMethodNode;
+import org.teavm.model.Instruction;
 import org.teavm.model.Program;
-import org.teavm.model.util.AsyncProgramSplitter;
+import org.teavm.model.Variable;
+import org.teavm.model.util.*;
 
 /**
  *
@@ -52,6 +56,9 @@ public class Optimizer {
     }
 
     public void optimize(AsyncMethodNode method, AsyncProgramSplitter splitter) {
+        LivenessAnalyzer liveness = new LivenessAnalyzer();
+        liveness.analyze(splitter.getOriginalProgram());
+
         boolean[] preservedVars = new boolean[method.getVariables().size()];
         int[][] readFrequencies = new int[splitter.size()][];
         for (int i = 0; i < splitter.size(); ++i) {
@@ -59,16 +66,19 @@ public class Optimizer {
             stats.analyze(splitter.getProgram(i));
             readFrequencies[i] = stats.reads;
             for (int j = 0; j < stats.writes.length; ++j) {
-                if (stats.readUninitialized[j] || stats.writes[j] != 1 && stats.reads[j] > 0) {
+                if (stats.writes[j] != 1 && stats.reads[j] > 0) {
                     preservedVars[j] = true;
                 }
             }
         }
+
         for (int i = 0; i < splitter.size(); ++i) {
+            boolean[] partPreservedVars = preservedVars.clone();
             AsyncMethodPart part = method.getBody().get(i);
             BreakEliminator breakEliminator = new BreakEliminator();
             breakEliminator.eliminate(part.getStatement());
-            OptimizingVisitor optimizer = new OptimizingVisitor(preservedVars, readFrequencies[i]);
+            findEscapingLiveVars(liveness, splitter, i, partPreservedVars);
+            OptimizingVisitor optimizer = new OptimizingVisitor(partPreservedVars, readFrequencies[i]);
             part.getStatement().acceptVisitor(optimizer);
             part.setStatement(optimizer.resultStmt);
         }
@@ -86,4 +96,45 @@ public class Optimizer {
             method.getVariables().set(i, i);
         }
     }
+
+    private void findEscapingLiveVars(LivenessAnalyzer liveness, AsyncProgramSplitter splitter, int partIndex,
+            boolean[] output) {
+        Program originalProgram = splitter.getOriginalProgram();
+        Graph cfg = ProgramUtils.buildControlFlowGraph(originalProgram);
+        int[] successors = splitter.getBlockSuccessors(partIndex);
+        int[] splitPoints = splitter.getSplitPoints(partIndex);
+
+        for (int i = 0; i < originalProgram.basicBlockCount(); ++i) {
+            if (successors[i] < 0) {
+                continue;
+            }
+
+            // Determine live-out vars
+            BitSet liveVars = new BitSet();
+            for (int succ : cfg.outgoingEdges(i)) {
+                liveVars.or(liveness.liveIn(succ));
+            }
+
+            // Remove from live set all variables that are defined in these blocks
+            DefinitionExtractor defExtractor = new DefinitionExtractor();
+            UsageExtractor useExtractor = new UsageExtractor();
+            List<Instruction> instructions = originalProgram.basicBlockAt(i).getInstructions();
+            int splitPoint = splitPoints[i];
+            for (int j = instructions.size() - 1; j >= splitPoint; --j) {
+                instructions.get(j).acceptVisitor(useExtractor);
+                instructions.get(j).acceptVisitor(defExtractor);
+                for (Variable var : useExtractor.getUsedVariables()) {
+                    liveVars.set(var.getIndex());
+                }
+                for (Variable var : defExtractor.getDefinedVariables()) {
+                    liveVars.clear(var.getIndex());
+                }
+            }
+
+            // Add live variables to output
+            for (int j = liveVars.nextSetBit(0); j >= 0; j = liveVars.nextSetBit(j + 1)) {
+                output[j] = true;
+            }
+        }
+    }
 }
diff --git a/teavm-core/src/main/java/org/teavm/javascript/ReadWriteStatsBuilder.java b/teavm-core/src/main/java/org/teavm/javascript/ReadWriteStatsBuilder.java
index 9b02c1e99..17d7666fb 100644
--- a/teavm-core/src/main/java/org/teavm/javascript/ReadWriteStatsBuilder.java
+++ b/teavm-core/src/main/java/org/teavm/javascript/ReadWriteStatsBuilder.java
@@ -31,7 +31,6 @@ import org.teavm.model.util.UsageExtractor;
 class ReadWriteStatsBuilder {
     public int[] reads;
     public int[] writes;
-    public boolean[] readUninitialized;
 
     private ReadWriteStatsBuilder() {
     }
@@ -39,7 +38,6 @@ class ReadWriteStatsBuilder {
     public ReadWriteStatsBuilder(int variableCount) {
         reads = new int[variableCount];
         writes = new int[variableCount];
-        readUninitialized = new boolean[variableCount];
     }
 
     public ReadWriteStatsBuilder copy() {
@@ -67,9 +65,6 @@ class ReadWriteStatsBuilder {
                 }
                 for (Variable var : useExtractor.getUsedVariables()) {
                     reads[var.getIndex()]++;
-                    if (writes[var.getIndex()] == 0) {
-                        readUninitialized[var.getIndex()] = true;
-                    }
                 }
             }
             for (Phi phi : block.getPhis()) {
diff --git a/teavm-core/src/main/java/org/teavm/model/util/AsyncProgramSplitter.java b/teavm-core/src/main/java/org/teavm/model/util/AsyncProgramSplitter.java
index e3b3ccde0..2c49e180e 100644
--- a/teavm-core/src/main/java/org/teavm/model/util/AsyncProgramSplitter.java
+++ b/teavm-core/src/main/java/org/teavm/model/util/AsyncProgramSplitter.java
@@ -31,6 +31,7 @@ public class AsyncProgramSplitter {
     private Map<Long, Integer> partMap = new HashMap<>();
     private ClassReaderSource classSource;
     private Set<MethodReference> asyncMethods = new HashSet<>();
+    private Program program;
 
     public AsyncProgramSplitter(ClassReaderSource classSource, Set<MethodReference> asyncMethods) {
         this.classSource = classSource;
@@ -38,12 +39,15 @@ public class AsyncProgramSplitter {
     }
 
     public void split(Program program) {
+        this.program = program;
         parts.clear();
         Program initialProgram = createStubCopy(program);
         Part initialPart = new Part();
         initialPart.program = initialProgram;
         initialPart.blockSuccessors = new int[program.basicBlockCount()];
         Arrays.fill(initialPart.blockSuccessors, -1);
+        initialPart.splitPoints = new int[program.basicBlockCount()];
+        Arrays.fill(initialPart.splitPoints, -1);
         parts.add(initialPart);
         partMap.put(0L, 0);
         Step initialStep = new Step();
@@ -87,6 +91,8 @@ public class AsyncProgramSplitter {
                 }
                 last = i;
 
+                step.targetPart.splitPoints[step.source] = i;
+
                 // If this instruction already separates program, end with current block and refer to the
                 // existing part
                 long key = ((long)step.source << 32) | i;
@@ -103,6 +109,8 @@ public class AsyncProgramSplitter {
                 parts.add(part);
                 part.blockSuccessors = new int[program.basicBlockCount() + 1];
                 Arrays.fill(part.blockSuccessors, -1);
+                part.splitPoints = new int[program.basicBlockCount() + 1];
+                Arrays.fill(part.splitPoints, -1);
 
                 // Mark current instruction as a separator and remember which part is in charge.
                 partMap.put(key, partId);
@@ -192,6 +200,10 @@ public class AsyncProgramSplitter {
         return parts.size();
     }
 
+    public Program getOriginalProgram() {
+        return program;
+    }
+
     public Program getProgram(int index) {
         return parts.get(index).program;
     }
@@ -201,9 +213,18 @@ public class AsyncProgramSplitter {
         return Arrays.copyOf(result, result.length);
     }
 
+    public int getBlockSuccessor(int index, int blockIndex) {
+        return parts.get(index).blockSuccessors[blockIndex];
+    }
+
+    public int[] getSplitPoints(int index) {
+        return parts.get(index).splitPoints.clone();
+    }
+
     private static class Part {
         Program program;
         int[] blockSuccessors;
+        int[] splitPoints;
     }
 
     private static class Step {
diff --git a/teavm-core/src/main/java/org/teavm/model/util/DefinitionExtractor.java b/teavm-core/src/main/java/org/teavm/model/util/DefinitionExtractor.java
index 7cca20ed0..fec90ad2e 100644
--- a/teavm-core/src/main/java/org/teavm/model/util/DefinitionExtractor.java
+++ b/teavm-core/src/main/java/org/teavm/model/util/DefinitionExtractor.java
@@ -205,11 +205,11 @@ public class DefinitionExtractor implements InstructionVisitor {
 
     @Override
     public void visit(MonitorEnterInstruction insn) {
-        
+        definedVariables = new Variable[0];
     }
 
     @Override
     public void visit(MonitorExitInstruction insn) {
-        
+        definedVariables = new Variable[0];
     }
 }
diff --git a/teavm-samples/teavm-samples-async/pom.xml b/teavm-samples/teavm-samples-async/pom.xml
index 99a38de06..5805851ee 100644
--- a/teavm-samples/teavm-samples-async/pom.xml
+++ b/teavm-samples/teavm-samples-async/pom.xml
@@ -65,7 +65,7 @@
               <targetDirectory>${project.build.directory}/generated/js/teavm</targetDirectory>
               <mainClass>org.teavm.samples.async.AsyncProgram</mainClass>
               <runtime>SEPARATE</runtime>
-              <minifying>true</minifying>
+              <minifying>false</minifying>
               <debugInformationGenerated>true</debugInformationGenerated>
               <sourceMapsGenerated>true</sourceMapsGenerated>
               <sourceFilesCopied>true</sourceFilesCopied>