diff --git a/core/src/main/java/org/teavm/common/DefaultGraphSplittingBackend.java b/core/src/main/java/org/teavm/common/DefaultGraphSplittingBackend.java
index 3a2453123..44f774568 100644
--- a/core/src/main/java/org/teavm/common/DefaultGraphSplittingBackend.java
+++ b/core/src/main/java/org/teavm/common/DefaultGraphSplittingBackend.java
@@ -18,10 +18,6 @@ package org.teavm.common;
 import com.carrotsearch.hppc.IntIntMap;
 import com.carrotsearch.hppc.IntIntOpenHashMap;
 
-/**
- *
- * @author Alexey Andreev
- */
 public class DefaultGraphSplittingBackend implements GraphSplittingBackend {
     private MutableDirectedGraph graph;
     private int index;
@@ -49,10 +45,6 @@ public class DefaultGraphSplittingBackend implements GraphSplittingBackend {
         return prototypeNodes.get(index);
     }
 
-    public int copyIndex(int index) {
-        return copyIndexes.get(index);
-    }
-
     @Override
     public int[] split(int[] domain, int[] nodes) {
         int[] copies = new int[nodes.length];
diff --git a/core/src/main/java/org/teavm/common/GraphSplittingBackend.java b/core/src/main/java/org/teavm/common/GraphSplittingBackend.java
index 791764e76..42fe9d91d 100644
--- a/core/src/main/java/org/teavm/common/GraphSplittingBackend.java
+++ b/core/src/main/java/org/teavm/common/GraphSplittingBackend.java
@@ -15,10 +15,6 @@
  */
 package org.teavm.common;
 
-/**
- *
- * @author Alexey Andreev
- */
 public interface GraphSplittingBackend {
     int[] split(int[] domain, int[] nodes);
 }
diff --git a/core/src/main/java/org/teavm/common/GraphUtils.java b/core/src/main/java/org/teavm/common/GraphUtils.java
index eb2bc06cb..365d1fd11 100644
--- a/core/src/main/java/org/teavm/common/GraphUtils.java
+++ b/core/src/main/java/org/teavm/common/GraphUtils.java
@@ -19,6 +19,7 @@ import java.util.ArrayList;
 import java.util.Arrays;
 import java.util.List;
 import java.util.function.IntPredicate;
+import java.util.stream.Collectors;
 
 /**
  *
@@ -371,4 +372,16 @@ public final class GraphUtils {
         }
         return set;
     }
+
+    public static String printToDot(Graph graph) {
+        StringBuilder sb = new StringBuilder("digraph G {\n");
+        for (int i = 0; i < graph.size(); ++i) {
+            String successors = Arrays.stream(graph.outgoingEdges(i))
+                    .mapToObj(String::valueOf)
+                    .collect(Collectors.joining(", "));
+            sb.append("  ").append(i).append(" -> {").append(successors).append("}\n");
+        }
+        sb.append("}");
+        return sb.toString();
+    }
 }
diff --git a/core/src/main/java/org/teavm/common/IrreducibleGraphConverter.java b/core/src/main/java/org/teavm/common/IrreducibleGraphConverter.java
index ec8a79003..17cd3fe83 100644
--- a/core/src/main/java/org/teavm/common/IrreducibleGraphConverter.java
+++ b/core/src/main/java/org/teavm/common/IrreducibleGraphConverter.java
@@ -32,9 +32,19 @@ class IrreducibleGraphConverter {
     private Graph cfg;
     private int totalNodeCount;
     private GraphSplittingBackend backend;
+    private IntSet[] nodeCopies;
+    private IntegerArray nodeOriginals;
 
     public void convertToReducible(Graph cfg, int[] weight, GraphSplittingBackend backend) {
         this.backend = backend;
+
+        nodeCopies = new IntOpenHashSet[cfg.size()];
+        nodeOriginals = new IntegerArray(cfg.size());
+        for (int i = 0; i < cfg.size(); ++i) {
+            nodeCopies[i] = new IntOpenHashSet();
+            nodeOriginals.add(i);
+        }
+
         int[][] identityNodeMap = new int[cfg.size()][];
         for (int i = 0; i < identityNodeMap.length; ++i) {
             identityNodeMap[i] = new int[] { i };
@@ -163,7 +173,11 @@ class IrreducibleGraphConverter {
         }
 
         // Delegate splitting to domain
-        int[][] newNodes = unflatten(backend.split(flatten(mappedDomain), flatten(mappedNonDomain)), mappedNonDomain);
+        int[] nodesToCopy = withCopies(flatten(mappedNonDomain));
+        int[] copies = backend.split(withCopies(flatten(mappedDomain)), nodesToCopy);
+        registerCopies(nodesToCopy, copies);
+
+        int[][] newNodes = unflatten(withoutCopies(copies), mappedNonDomain);
         for (int[] nodes : newNodes) {
             totalNodeCount += nodes.length;
         }
@@ -231,6 +245,50 @@ class IrreducibleGraphConverter {
         handleLoops(new DJGraph(builder.build(), mappedWeight), newNodeMap);
     }
 
+    private int[] withCopies(int[] nodes) {
+        IntegerArray nodesWithCopies = new IntegerArray(nodes.length);
+        for (int node : nodes) {
+            nodesWithCopies.add(node);
+            IntSet copies = nodeCopies[node];
+            if (copies != null) {
+                nodesWithCopies.addAll(copies.toArray());
+            }
+        }
+        return nodesWithCopies.getAll();
+    }
+
+    private int[] withoutCopies(int[] nodesWithCopies) {
+        IntSet visited = new IntOpenHashSet();
+        int[] nodes = new int[nodesWithCopies.length];
+        int sz = 0;
+        for (int node : nodesWithCopies) {
+            node = nodeOriginals.get(node);
+            if (visited.add(node)) {
+                nodes[sz++] = node;
+            }
+        }
+        return Arrays.copyOf(nodes, sz);
+    }
+
+    private void registerCopies(int[] originalNodes, int[] copies) {
+        for (int i = 0; i < originalNodes.length; ++i) {
+            int original = nodeOriginals.get(originalNodes[i]);
+            int copy = copies[i];
+            IntSet knownCopies = nodeCopies[original];
+            if (knownCopies == null) {
+                knownCopies = new IntOpenHashSet();
+                nodeCopies[original] = knownCopies;
+            }
+
+            if (knownCopies.add(copy)) {
+                while (nodeOriginals.size() <= copy) {
+                    nodeOriginals.add(-1);
+                }
+                nodeOriginals.set(copy, original);
+            }
+        }
+    }
+
     private void collapse(DJGraph djGraph, int[] scc, int[][] nodeMap) {
         int cls = djGraph.collapse(scc);
         IntegerArray nodes = new IntegerArray(djGraph.getGraph().size());
diff --git a/core/src/main/java/org/teavm/model/util/ProgramNodeSplittingBackend.java b/core/src/main/java/org/teavm/model/util/ProgramNodeSplittingBackend.java
index 7369f7c38..3584ee3b5 100644
--- a/core/src/main/java/org/teavm/model/util/ProgramNodeSplittingBackend.java
+++ b/core/src/main/java/org/teavm/model/util/ProgramNodeSplittingBackend.java
@@ -21,10 +21,6 @@ import org.teavm.common.GraphSplittingBackend;
 import org.teavm.model.BasicBlock;
 import org.teavm.model.Program;
 
-/**
- *
- * @author Alexey Andreev
- */
 public class ProgramNodeSplittingBackend implements GraphSplittingBackend {
     private Program program;
 
diff --git a/core/src/test/java/org/teavm/common/GraphTest.java b/core/src/test/java/org/teavm/common/GraphTest.java
index 10632d610..ffddbf5bd 100644
--- a/core/src/test/java/org/teavm/common/GraphTest.java
+++ b/core/src/test/java/org/teavm/common/GraphTest.java
@@ -26,10 +26,6 @@ import java.util.Comparator;
 import java.util.function.IntPredicate;
 import org.junit.Test;
 
-/**
- *
- * @author Alexey Andreev
- */
 public class GraphTest {
     @Test
     public void stronglyConnectedComponentsCalculated() {
@@ -205,7 +201,6 @@ public class GraphTest {
         builder.addEdge(7, 8);
         builder.addEdge(8, 7);
         Graph graph = builder.build();
-
         DefaultGraphSplittingBackend backend = new DefaultGraphSplittingBackend(graph);
         int[] weights = new int[graph.size()];
         Arrays.fill(weights, 1);
@@ -214,7 +209,7 @@ public class GraphTest {
 
         assertTrue("Should be irreducible", GraphUtils.isIrreducible(graph));
         assertFalse("Should be reducible", GraphUtils.isIrreducible(result));
-        assertTrue("Should be equialent", isEquialent(backend, graph));
+        assertTrue("Should be equivalent", isEquialent(backend, graph));
     }
 
     private boolean isEquialent(DefaultGraphSplittingBackend backend, Graph proto) {