diff --git a/classlib/src/main/java/org/teavm/classlib/impl/IntegerUtil.java b/classlib/src/main/java/org/teavm/classlib/impl/IntegerUtil.java
new file mode 100644
index 000000000..ad4329e2f
--- /dev/null
+++ b/classlib/src/main/java/org/teavm/classlib/impl/IntegerUtil.java
@@ -0,0 +1,43 @@
+/*
+ *  Copyright 2018 Alexey Andreev.
+ *
+ *  Licensed under the Apache License, Version 2.0 (the "License");
+ *  you may not use this file except in compliance with the License.
+ *  You may obtain a copy of the License at
+ *
+ *       http://www.apache.org/licenses/LICENSE-2.0
+ *
+ *  Unless required by applicable law or agreed to in writing, software
+ *  distributed under the License is distributed on an "AS IS" BASIS,
+ *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ *  See the License for the specific language governing permissions and
+ *  limitations under the License.
+ */
+package org.teavm.classlib.impl;
+
+import org.teavm.classlib.java.lang.TCharacter;
+
+public final class IntegerUtil {
+    private IntegerUtil() {
+    }
+
+    public static String toUnsignedLogRadixString(int value, int radixLog2, int size) {
+        if (value == 0) {
+            return "0";
+        }
+
+        int radix = 1 << radixLog2;
+        int mask = radix - 1;
+        int sz = (size - Integer.numberOfLeadingZeros(value) + radixLog2 - 1) / radixLog2;
+        char[] chars = new char[sz];
+
+        int pos = (sz - 1) * radixLog2;
+        int target = 0;
+        while (pos >= 0) {
+            chars[target++] = TCharacter.forDigit((value >>> pos) & mask, radix);
+            pos -= radixLog2;
+        }
+
+        return new String(chars);
+    }
+}
diff --git a/classlib/src/main/java/org/teavm/classlib/java/lang/TInteger.java b/classlib/src/main/java/org/teavm/classlib/java/lang/TInteger.java
index 42ac0f1dd..ab8f82b1f 100644
--- a/classlib/src/main/java/org/teavm/classlib/java/lang/TInteger.java
+++ b/classlib/src/main/java/org/teavm/classlib/java/lang/TInteger.java
@@ -15,6 +15,8 @@
  */
 package org.teavm.classlib.java.lang;
 
+import static org.teavm.classlib.impl.IntegerUtil.toUnsignedLogRadixString;
+
 public class TInteger extends TNumber implements TComparable<TInteger> {
     public static final int SIZE = 32;
     public static final int MIN_VALUE = 0x80000000;
@@ -39,15 +41,15 @@ public class TInteger extends TNumber implements TComparable<TInteger> {
     }
 
     public static String toHexString(int i) {
-        return toString(i, 16);
+        return toUnsignedLogRadixString(i, 4, SIZE);
     }
 
     public static String toOctalString(int i) {
-        return toString(i, 8);
+        return toUnsignedLogRadixString(i, 3, SIZE);
     }
 
     public static String toBinaryString(int i) {
-        return toString(i, 2);
+        return toUnsignedLogRadixString(i, 1, SIZE);
     }
 
     public static String toString(int i) {
diff --git a/classlib/src/main/java/org/teavm/classlib/java/lang/TLong.java b/classlib/src/main/java/org/teavm/classlib/java/lang/TLong.java
index fd92e87bc..72225116c 100644
--- a/classlib/src/main/java/org/teavm/classlib/java/lang/TLong.java
+++ b/classlib/src/main/java/org/teavm/classlib/java/lang/TLong.java
@@ -172,15 +172,35 @@ public class TLong extends TNumber implements TComparable<TLong> {
     }
 
     public static String toHexString(long i) {
-        return toString(i, 16);
+        return toUnsignedLogRadixString(i, 4);
     }
 
     public static String toOctalString(long i) {
-        return toString(i, 8);
+        return toUnsignedLogRadixString(i, 3);
     }
 
     public static String toBinaryString(long i) {
-        return toString(i, 2);
+        return toUnsignedLogRadixString(i, 1);
+    }
+
+    private static String toUnsignedLogRadixString(long value, int radixLog2) {
+        if (value == 0) {
+            return "0";
+        }
+
+        int radix = 1 << radixLog2;
+        int mask = radix - 1;
+        int sz = (SIZE - numberOfLeadingZeros(value) + radixLog2 - 1) / radixLog2;
+        char[] chars = new char[sz];
+
+        long pos = (sz - 1) * radixLog2;
+        int target = 0;
+        while (pos >= 0) {
+            chars[target++] = TCharacter.forDigit((int) (value >>> pos) & mask, radix);
+            pos -= radixLog2;
+        }
+
+        return new String(chars);
     }
 
     public static String toString(long value) {
diff --git a/tests/src/test/java/org/teavm/classlib/java/lang/IntegerTest.java b/tests/src/test/java/org/teavm/classlib/java/lang/IntegerTest.java
index 5f92545b6..58accc4f6 100644
--- a/tests/src/test/java/org/teavm/classlib/java/lang/IntegerTest.java
+++ b/tests/src/test/java/org/teavm/classlib/java/lang/IntegerTest.java
@@ -150,4 +150,14 @@ public class IntegerTest {
         assertNull(Integer.getInteger("test.baz"));
         assertNull(Integer.getInteger(null));
     }
+
+    @Test
+    public void toHex() {
+        assertEquals("0", Integer.toHexString(0));
+        assertEquals("1", Integer.toHexString(1));
+        assertEquals("a", Integer.toHexString(10));
+        assertEquals("11", Integer.toHexString(17));
+        assertEquals("ff", Integer.toHexString(255));
+        assertEquals("ffffffff", Integer.toHexString(-1));
+    }
 }