diff --git a/core/src/main/java/org/teavm/callgraph/DefaultCallGraph.java b/core/src/main/java/org/teavm/callgraph/DefaultCallGraph.java
index 1819c6192..865f37110 100644
--- a/core/src/main/java/org/teavm/callgraph/DefaultCallGraph.java
+++ b/core/src/main/java/org/teavm/callgraph/DefaultCallGraph.java
@@ -15,58 +15,98 @@
  */
 package org.teavm.callgraph;
 
+import java.io.IOException;
+import java.io.ObjectInputStream;
+import java.io.ObjectOutputStream;
+import java.io.Serializable;
 import java.util.*;
 import org.teavm.model.FieldReference;
 import org.teavm.model.MethodReference;
 
-/**
- *
- * @author Alexey Andreev
- */
-public class DefaultCallGraph implements CallGraph {
-    private Map<MethodReference, DefaultCallGraphNode> nodes = new HashMap<>();
-    private Map<FieldReference, Set<DefaultFieldAccessSite>> fieldAccessSites = new HashMap<>();
-    private Map<String, Set<DefaultClassAccessSite>> classAccessSites = new HashMap<>();
+public class DefaultCallGraph implements CallGraph, Serializable {
+    private transient Map<MethodReference, DefaultCallGraphNode> nodes = new HashMap<>();
+    private List<Map.Entry<MethodReference, DefaultCallGraphNode>> nodeList;
+    private transient Map<FieldReference, Set<DefaultFieldAccessSite>> fieldAccessSites = new HashMap<>();
+    private List<Map.Entry<FieldReference, DefaultFieldAccessSite>> fieldAccessSiteList;
+    private transient Map<String, Set<DefaultClassAccessSite>> classAccessSites = new HashMap<>();
+    private List<Map.Entry<String, DefaultClassAccessSite>> classAccessSiteList;
 
     @Override
     public DefaultCallGraphNode getNode(MethodReference method) {
-        DefaultCallGraphNode node = nodes.get(method);
-        if (node == null) {
-            node = new DefaultCallGraphNode(this, method);
-            nodes.put(method, node);
-        }
-        return nodes.get(method);
+        ensureDeserialized();
+        return nodes.computeIfAbsent(method, k -> new DefaultCallGraphNode(this, method));
     }
 
     @Override
     public Collection<DefaultFieldAccessSite> getFieldAccess(FieldReference reference) {
+        ensureDeserialized();
         Set<DefaultFieldAccessSite> resultSet = fieldAccessSites.get(reference);
-        return resultSet != null ? Collections.unmodifiableSet(resultSet)
-                : Collections.<DefaultFieldAccessSite>emptySet();
+        return resultSet != null ? Collections.unmodifiableSet(resultSet) : Collections.emptySet();
     }
 
     void addFieldAccess(DefaultFieldAccessSite accessSite) {
-        Set<DefaultFieldAccessSite> sites = fieldAccessSites.get(accessSite.getField());
-        if (sites == null) {
-            sites = new HashSet<>();
-            fieldAccessSites.put(accessSite.getField(), sites);
-        }
-        sites.add(accessSite);
+        ensureDeserialized();
+        fieldAccessSites.computeIfAbsent(accessSite.getField(), k -> new HashSet<>()).add(accessSite);
     }
 
     @Override
     public Collection<DefaultClassAccessSite> getClassAccess(String className) {
+        ensureDeserialized();
         Set<DefaultClassAccessSite> resultSet = classAccessSites.get(className);
-        return resultSet != null ? Collections.unmodifiableSet(resultSet)
-                : Collections.<DefaultClassAccessSite>emptySet();
+        return resultSet != null ? Collections.unmodifiableSet(resultSet) : Collections.emptySet();
     }
 
     void addClassAccess(DefaultClassAccessSite accessSite) {
-        Set<DefaultClassAccessSite> sites = classAccessSites.get(accessSite.getClassName());
-        if (sites == null) {
-            sites = new HashSet<>();
-            classAccessSites.put(accessSite.getClassName(), sites);
+        ensureDeserialized();
+        classAccessSites.computeIfAbsent(accessSite.getClassName(), k -> new HashSet<>()).add(accessSite);
+    }
+
+    private void ensureDeserialized() {
+        if (nodes != null) {
+            return;
         }
-        sites.add(accessSite);
+
+        nodes = new HashMap<>();
+        for (Map.Entry<MethodReference, DefaultCallGraphNode> entry : nodeList) {
+            nodes.put(entry.getKey(), entry.getValue());
+        }
+        nodeList = null;
+
+        fieldAccessSites = new HashMap<>();
+        for (Map.Entry<FieldReference, DefaultFieldAccessSite> entry : fieldAccessSiteList) {
+            fieldAccessSites.computeIfAbsent(entry.getKey(), k -> new HashSet<>()).add(entry.getValue());
+        }
+        fieldAccessSiteList = null;
+
+        classAccessSites = new HashMap<>();
+        for (Map.Entry<String, DefaultClassAccessSite> entry : classAccessSiteList) {
+            classAccessSites.computeIfAbsent(entry.getKey(), k -> new HashSet<>()).add(entry.getValue());
+        }
+        classAccessSiteList = null;
+    }
+
+    private void writeObject(ObjectOutputStream out) throws IOException {
+        ensureDeserialized();
+        nodeList = new ArrayList<>(nodes.entrySet());
+
+        fieldAccessSiteList = new ArrayList<>();
+        for (Map.Entry<FieldReference, Set<DefaultFieldAccessSite>> entry : fieldAccessSites.entrySet()) {
+            for (DefaultFieldAccessSite site : entry.getValue()) {
+                fieldAccessSiteList.add(new AbstractMap.SimpleEntry<>(entry.getKey(), site));
+            }
+        }
+
+        classAccessSiteList = new ArrayList<>();
+        for (Map.Entry<String, Set<DefaultClassAccessSite>> entry : classAccessSites.entrySet()) {
+            for (DefaultClassAccessSite site : entry.getValue()) {
+                classAccessSiteList.add(new AbstractMap.SimpleEntry<>(entry.getKey(), site));
+            }
+        }
+
+        out.defaultWriteObject();
+    }
+
+    private void readObject(ObjectInputStream in) throws IOException, ClassNotFoundException {
+        in.defaultReadObject();
     }
 }
diff --git a/core/src/main/java/org/teavm/callgraph/DefaultCallGraphNode.java b/core/src/main/java/org/teavm/callgraph/DefaultCallGraphNode.java
index f1563c57d..33e153a30 100644
--- a/core/src/main/java/org/teavm/callgraph/DefaultCallGraphNode.java
+++ b/core/src/main/java/org/teavm/callgraph/DefaultCallGraphNode.java
@@ -15,6 +15,10 @@
  */
 package org.teavm.callgraph;
 
+import java.io.IOException;
+import java.io.ObjectInputStream;
+import java.io.ObjectOutputStream;
+import java.io.Serializable;
 import java.util.ArrayList;
 import java.util.Collection;
 import java.util.Collections;
@@ -25,20 +29,19 @@ import org.teavm.model.FieldReference;
 import org.teavm.model.MethodReference;
 import org.teavm.model.TextLocation;
 
-/**
- *
- * @author Alexey Andreev
- */
-public class DefaultCallGraphNode implements CallGraphNode {
+public class DefaultCallGraphNode implements CallGraphNode, Serializable {
     private DefaultCallGraph graph;
     private MethodReference method;
-    private Set<DefaultCallSite> callSites = new HashSet<>();
+    private transient Set<DefaultCallSite> callSites = new HashSet<>();
+    private List<DefaultCallSite> callSiteList;
     private transient Set<DefaultCallSite> safeCallSites;
     private List<DefaultCallSite> callerCallSites = new ArrayList<>();
     private transient List<DefaultCallSite> safeCallersCallSites;
-    private Set<DefaultFieldAccessSite> fieldAccessSites = new HashSet<>();
+    private transient Set<DefaultFieldAccessSite> fieldAccessSites = new HashSet<>();
+    private List<DefaultFieldAccessSite> fieldAccessSiteList;
     private transient Set<DefaultFieldAccessSite> safeFieldAccessSites;
-    private Set<DefaultClassAccessSite> classAccessSites = new HashSet<>();
+    private transient Set<DefaultClassAccessSite> classAccessSites = new HashSet<>();
+    private List<DefaultClassAccessSite> classAccessSiteList;
     private transient Set<DefaultClassAccessSite> safeClassAccessSites;
 
     DefaultCallGraphNode(DefaultCallGraph graph, MethodReference method) {
@@ -58,6 +61,7 @@ public class DefaultCallGraphNode implements CallGraphNode {
 
     @Override
     public Collection<DefaultCallSite> getCallSites() {
+        ensureDeserialized();
         if (safeCallSites == null) {
             safeCallSites = Collections.unmodifiableSet(callSites);
         }
@@ -66,6 +70,7 @@ public class DefaultCallGraphNode implements CallGraphNode {
 
     @Override
     public Collection<DefaultCallSite> getCallerCallSites() {
+        ensureDeserialized();
         if (safeCallersCallSites == null) {
             safeCallersCallSites = Collections.unmodifiableList(callerCallSites);
         }
@@ -73,6 +78,7 @@ public class DefaultCallGraphNode implements CallGraphNode {
     }
 
     public boolean addCallSite(MethodReference method, TextLocation location) {
+        ensureDeserialized();
         DefaultCallGraphNode callee = graph.getNode(method);
         DefaultCallSite callSite = new DefaultCallSite(location, callee, this);
         if (callSites.add(callSite)) {
@@ -89,6 +95,7 @@ public class DefaultCallGraphNode implements CallGraphNode {
 
     @Override
     public Collection<DefaultFieldAccessSite> getFieldAccessSites() {
+        ensureDeserialized();
         if (safeFieldAccessSites == null) {
             safeFieldAccessSites = Collections.unmodifiableSet(fieldAccessSites);
         }
@@ -96,6 +103,7 @@ public class DefaultCallGraphNode implements CallGraphNode {
     }
 
     public boolean addFieldAccess(FieldReference field, TextLocation location) {
+        ensureDeserialized();
         DefaultFieldAccessSite site = new DefaultFieldAccessSite(location, this, field);
         if (fieldAccessSites.add(site)) {
             graph.addFieldAccess(site);
@@ -107,6 +115,7 @@ public class DefaultCallGraphNode implements CallGraphNode {
 
     @Override
     public Collection<? extends ClassAccessSite> getClassAccessSites() {
+        ensureDeserialized();
         if (safeClassAccessSites == null) {
             safeClassAccessSites = Collections.unmodifiableSet(classAccessSites);
         }
@@ -114,6 +123,7 @@ public class DefaultCallGraphNode implements CallGraphNode {
     }
 
     public boolean addClassAccess(String className, TextLocation location) {
+        ensureDeserialized();
         DefaultClassAccessSite site = new DefaultClassAccessSite(location, this, className);
         if (classAccessSites.add(site)) {
             graph.addClassAccess(site);
@@ -122,4 +132,31 @@ public class DefaultCallGraphNode implements CallGraphNode {
             return false;
         }
     }
+
+    private void ensureDeserialized() {
+        if (callSites != null) {
+            return;
+        }
+
+        callSites = new HashSet<>(callSiteList);
+        callSiteList = null;
+
+        fieldAccessSites = new HashSet<>(fieldAccessSiteList);
+        fieldAccessSiteList = null;
+
+        classAccessSites = new HashSet<>(classAccessSiteList);
+        classAccessSiteList = null;
+    }
+
+    private void writeObject(ObjectOutputStream out) throws IOException {
+        ensureDeserialized();
+        callSiteList = new ArrayList<>(callSites);
+        fieldAccessSiteList = new ArrayList<>(fieldAccessSites);
+        classAccessSiteList = new ArrayList<>(classAccessSites);
+        out.defaultWriteObject();
+    }
+
+    private void readObject(ObjectInputStream in) throws IOException, ClassNotFoundException {
+        in.defaultReadObject();
+    }
 }
diff --git a/core/src/main/java/org/teavm/callgraph/DefaultCallSite.java b/core/src/main/java/org/teavm/callgraph/DefaultCallSite.java
index 6cb40f152..1e22993c7 100644
--- a/core/src/main/java/org/teavm/callgraph/DefaultCallSite.java
+++ b/core/src/main/java/org/teavm/callgraph/DefaultCallSite.java
@@ -15,14 +15,11 @@
  */
 package org.teavm.callgraph;
 
+import java.io.Serializable;
 import java.util.Objects;
 import org.teavm.model.TextLocation;
 
-/**
- *
- * @author Alexey Andreev
- */
-public class DefaultCallSite implements CallSite {
+public class DefaultCallSite implements CallSite, Serializable {
     private TextLocation location;
     private DefaultCallGraphNode callee;
     private DefaultCallGraphNode caller;
diff --git a/core/src/main/java/org/teavm/callgraph/DefaultClassAccessSite.java b/core/src/main/java/org/teavm/callgraph/DefaultClassAccessSite.java
index 85da4fdfa..afa679a44 100644
--- a/core/src/main/java/org/teavm/callgraph/DefaultClassAccessSite.java
+++ b/core/src/main/java/org/teavm/callgraph/DefaultClassAccessSite.java
@@ -15,14 +15,11 @@
  */
 package org.teavm.callgraph;
 
+import java.io.Serializable;
 import java.util.Objects;
 import org.teavm.model.TextLocation;
 
-/**
- *
- * @author Alexey Andreev
- */
-public class DefaultClassAccessSite implements ClassAccessSite {
+public class DefaultClassAccessSite implements ClassAccessSite, Serializable {
     private TextLocation location;
     private CallGraphNode callee;
     private String className;
diff --git a/core/src/main/java/org/teavm/callgraph/DefaultFieldAccessSite.java b/core/src/main/java/org/teavm/callgraph/DefaultFieldAccessSite.java
index 21cb13f18..b086e9d94 100644
--- a/core/src/main/java/org/teavm/callgraph/DefaultFieldAccessSite.java
+++ b/core/src/main/java/org/teavm/callgraph/DefaultFieldAccessSite.java
@@ -15,15 +15,12 @@
  */
 package org.teavm.callgraph;
 
+import java.io.Serializable;
 import java.util.Objects;
 import org.teavm.model.FieldReference;
 import org.teavm.model.TextLocation;
 
-/**
- *
- * @author Alexey Andreev
- */
-public class DefaultFieldAccessSite implements FieldAccessSite {
+public class DefaultFieldAccessSite implements FieldAccessSite, Serializable {
     private TextLocation location;
     private CallGraphNode callee;
     private FieldReference field;
diff --git a/core/src/main/java/org/teavm/diagnostics/Problem.java b/core/src/main/java/org/teavm/diagnostics/Problem.java
index ee35b6996..b310e154d 100644
--- a/core/src/main/java/org/teavm/diagnostics/Problem.java
+++ b/core/src/main/java/org/teavm/diagnostics/Problem.java
@@ -15,14 +15,11 @@
  */
 package org.teavm.diagnostics;
 
+import java.io.Serializable;
 import java.util.Arrays;
 import org.teavm.model.*;
 
-/**
- *
- * @author Alexey Andreev
- */
-public class Problem {
+public class Problem implements Serializable {
     private ProblemSeverity severity;
     private CallLocation location;
     private String text;
diff --git a/core/src/main/java/org/teavm/diagnostics/ProblemProvider.java b/core/src/main/java/org/teavm/diagnostics/ProblemProvider.java
index 8faa4e069..5aa38bcde 100644
--- a/core/src/main/java/org/teavm/diagnostics/ProblemProvider.java
+++ b/core/src/main/java/org/teavm/diagnostics/ProblemProvider.java
@@ -17,10 +17,6 @@ package org.teavm.diagnostics;
 
 import java.util.List;
 
-/**
- *
- * @author Alexey Andreev
- */
 public interface ProblemProvider {
     List<Problem> getProblems();
 
diff --git a/core/src/main/java/org/teavm/diagnostics/ProblemSeverity.java b/core/src/main/java/org/teavm/diagnostics/ProblemSeverity.java
index 6e270b944..b26acca95 100644
--- a/core/src/main/java/org/teavm/diagnostics/ProblemSeverity.java
+++ b/core/src/main/java/org/teavm/diagnostics/ProblemSeverity.java
@@ -15,11 +15,9 @@
  */
 package org.teavm.diagnostics;
 
-/**
- *
- * @author Alexey Andreev
- */
-public enum ProblemSeverity {
+import java.io.Serializable;
+
+public enum ProblemSeverity implements Serializable {
     ERROR,
     WARNING
 }
diff --git a/core/src/main/java/org/teavm/model/CallLocation.java b/core/src/main/java/org/teavm/model/CallLocation.java
index 5c753cd9a..0b00f3f8a 100644
--- a/core/src/main/java/org/teavm/model/CallLocation.java
+++ b/core/src/main/java/org/teavm/model/CallLocation.java
@@ -15,9 +15,10 @@
  */
 package org.teavm.model;
 
+import java.io.Serializable;
 import java.util.Objects;
 
-public class CallLocation {
+public class CallLocation implements Serializable {
     private MethodReference method;
     private TextLocation sourceLocation;
 
diff --git a/core/src/main/java/org/teavm/model/FieldReference.java b/core/src/main/java/org/teavm/model/FieldReference.java
index 5dc6ae891..a16cf6cb9 100644
--- a/core/src/main/java/org/teavm/model/FieldReference.java
+++ b/core/src/main/java/org/teavm/model/FieldReference.java
@@ -15,11 +15,9 @@
  */
 package org.teavm.model;
 
-/**
- *
- * @author Alexey Andreev
- */
-public class FieldReference {
+import java.io.Serializable;
+
+public class FieldReference implements Serializable {
     private String className;
     private String fieldName;
 
diff --git a/core/src/main/java/org/teavm/model/MethodReference.java b/core/src/main/java/org/teavm/model/MethodReference.java
index 104e70fd1..76abd8300 100644
--- a/core/src/main/java/org/teavm/model/MethodReference.java
+++ b/core/src/main/java/org/teavm/model/MethodReference.java
@@ -17,6 +17,7 @@ package org.teavm.model;
 
 import com.fasterxml.jackson.annotation.JsonCreator;
 import com.fasterxml.jackson.annotation.JsonValue;
+import java.io.Serializable;
 import java.util.Arrays;
 
 /**
@@ -30,7 +31,7 @@ import java.util.Arrays;
  *
  * @author Alexey Andreev
  */
-public class MethodReference {
+public class MethodReference implements Serializable {
     private String className;
     private String name;
     private ValueType[] signature;
diff --git a/core/src/main/java/org/teavm/model/PrimitiveType.java b/core/src/main/java/org/teavm/model/PrimitiveType.java
index 1c3ba2fce..83edda24c 100644
--- a/core/src/main/java/org/teavm/model/PrimitiveType.java
+++ b/core/src/main/java/org/teavm/model/PrimitiveType.java
@@ -15,11 +15,9 @@
  */
 package org.teavm.model;
 
-/**
- *
- * @author Alexey Andreev
- */
-public enum PrimitiveType {
+import java.io.Serializable;
+
+public enum PrimitiveType implements Serializable {
     BOOLEAN,
     CHARACTER,
     BYTE,
diff --git a/core/src/main/java/org/teavm/model/TextLocation.java b/core/src/main/java/org/teavm/model/TextLocation.java
index 9995d41ce..73675ef98 100644
--- a/core/src/main/java/org/teavm/model/TextLocation.java
+++ b/core/src/main/java/org/teavm/model/TextLocation.java
@@ -15,9 +15,10 @@
  */
 package org.teavm.model;
 
+import java.io.Serializable;
 import java.util.Objects;
 
-public class TextLocation {
+public class TextLocation implements Serializable {
     private String fileName;
     private int line = -1;
 
diff --git a/core/src/main/java/org/teavm/model/ValueType.java b/core/src/main/java/org/teavm/model/ValueType.java
index bf7fc948d..d554f643d 100644
--- a/core/src/main/java/org/teavm/model/ValueType.java
+++ b/core/src/main/java/org/teavm/model/ValueType.java
@@ -15,15 +15,11 @@
  */
 package org.teavm.model;
 
+import java.io.Serializable;
 import java.util.*;
 import java.util.stream.Collectors;
 
-
-/**
- *
- * @author Alexey Andreev
- */
-public abstract class ValueType {
+public abstract class ValueType implements Serializable {
     volatile String reprCache;
     private static final Map<Class<?>, ValueType> primitiveMap = new HashMap<>();
 
diff --git a/core/src/main/java/org/teavm/vm/TeaVMProgressFeedback.java b/core/src/main/java/org/teavm/vm/TeaVMProgressFeedback.java
index 54d7470ea..7fd870c11 100644
--- a/core/src/main/java/org/teavm/vm/TeaVMProgressFeedback.java
+++ b/core/src/main/java/org/teavm/vm/TeaVMProgressFeedback.java
@@ -15,11 +15,9 @@
  */
 package org.teavm.vm;
 
-/**
- *
- * @author Alexey Andreev
- */
-public enum TeaVMProgressFeedback {
+import java.io.Serializable;
+
+public enum TeaVMProgressFeedback implements Serializable {
     CONTINUE,
     CANCEL
 }