diff --git a/teavm-classlib/src/main/java/org/teavm/classlib/java/lang/StringBuilderTests.java b/teavm-classlib/src/main/java/org/teavm/classlib/java/lang/StringBuilderTests.java
index 293eaeebe..0871b3da2 100644
--- a/teavm-classlib/src/main/java/org/teavm/classlib/java/lang/StringBuilderTests.java
+++ b/teavm-classlib/src/main/java/org/teavm/classlib/java/lang/StringBuilderTests.java
@@ -8,6 +8,7 @@ import org.junit.Test;
  * @author Alexey Andreev
  */
 public class StringBuilderTests {
+    @Test
     public void integerAppended() {
         StringBuilder sb = new StringBuilder();
         sb.append(23);
@@ -35,6 +36,34 @@ public class StringBuilderTests {
         assertEquals("2147483647", sb.toString());
     }
 
+    @Test
+    public void longAppended() {
+        StringBuilder sb = new StringBuilder();
+        sb.append(23L);
+        assertEquals("23", sb.toString());
+    }
+
+    @Test
+    public void negativeLongAppended() {
+        StringBuilder sb = new StringBuilder();
+        sb.append(-23L);
+        assertEquals("-23", sb.toString());
+    }
+
+    @Test
+    public void largeLongAppended() {
+        StringBuilder sb = new StringBuilder();
+        sb.append(12345678901234L);
+        assertEquals("12345678901234", sb.toString());
+    }
+
+    @Test
+    public void maxLongAppended() {
+        StringBuilder sb = new StringBuilder();
+        sb.append(9223372036854775807L);
+        assertEquals("9223372036854775807", sb.toString());
+    }
+
     @Test
     public void appendsCodePoint() {
         StringBuilder sb = new StringBuilder();
diff --git a/teavm-classlib/src/main/java/org/teavm/classlib/java/lang/TAbstractStringBuilder.java b/teavm-classlib/src/main/java/org/teavm/classlib/java/lang/TAbstractStringBuilder.java
index 5e0d210c6..305fbceb8 100644
--- a/teavm-classlib/src/main/java/org/teavm/classlib/java/lang/TAbstractStringBuilder.java
+++ b/teavm-classlib/src/main/java/org/teavm/classlib/java/lang/TAbstractStringBuilder.java
@@ -67,6 +67,43 @@ class TAbstractStringBuilder extends TObject implements TSerializable, TCharSequ
         return this;
     }
 
+    protected TAbstractStringBuilder append(long value) {
+        boolean positive = true;
+        if (value < 0) {
+            positive = false;
+            value = -value;
+        }
+        if (value < 10) {
+            if (!positive) {
+                ensureCapacity(length + 2);
+                buffer[length++] = '-';
+            } else {
+                ensureCapacity(length + 1);
+            }
+            buffer[length++] = (char)('0' + value);
+        } else {
+            int pos = 10;
+            int sz = 1;
+            while (pos < 1000000000000000000L && pos * 10 <= value) {
+                pos *= 10;
+                ++sz;
+            }
+            if (!positive) {
+                ++sz;
+            }
+            ensureCapacity(length + sz);
+            if (!positive) {
+                buffer[length++] = '-';
+            }
+            while (pos > 0) {
+                buffer[length++] = (char)('0' + value / pos);
+                value %= pos;
+                pos /= 10;
+            }
+        }
+        return this;
+    }
+
     protected TAbstractStringBuilder append(char c) {
         ensureCapacity(length + 1);
         buffer[length++] = c;
diff --git a/teavm-classlib/src/main/java/org/teavm/classlib/java/lang/TString.java b/teavm-classlib/src/main/java/org/teavm/classlib/java/lang/TString.java
index 0a66d0d8d..5138d6c1f 100644
--- a/teavm-classlib/src/main/java/org/teavm/classlib/java/lang/TString.java
+++ b/teavm-classlib/src/main/java/org/teavm/classlib/java/lang/TString.java
@@ -415,8 +415,12 @@ public class TString extends TObject implements TSerializable, TComparable<TStri
         return new TString(new char[] { c });
     }
 
-    public static TString valueOf(int index) {
-        return new TStringBuilder().append(index).toString0();
+    public static TString valueOf(int i) {
+        return new TStringBuilder().append(i).toString0();
+    }
+
+    public static TString valueOf(long l) {
+        return new TStringBuilder().append(l).toString0();
     }
 
     @Override
diff --git a/teavm-classlib/src/main/java/org/teavm/classlib/java/lang/TStringBuilder.java b/teavm-classlib/src/main/java/org/teavm/classlib/java/lang/TStringBuilder.java
index 62dbee60d..a24c67af6 100644
--- a/teavm-classlib/src/main/java/org/teavm/classlib/java/lang/TStringBuilder.java
+++ b/teavm-classlib/src/main/java/org/teavm/classlib/java/lang/TStringBuilder.java
@@ -17,6 +17,12 @@ public class TStringBuilder extends TAbstractStringBuilder {
         return this;
     }
 
+    @Override
+    public TStringBuilder append(long value) {
+        super.append(value);
+        return this;
+    }
+
     @Override
     public TStringBuilder append(char c) {
         super.append(c);