diff --git a/classlib/src/main/java/org/teavm/classlib/java/lang/TAbstractStringBuilder.java b/classlib/src/main/java/org/teavm/classlib/java/lang/TAbstractStringBuilder.java
index b85010fb2..a7cf112bc 100644
--- a/classlib/src/main/java/org/teavm/classlib/java/lang/TAbstractStringBuilder.java
+++ b/classlib/src/main/java/org/teavm/classlib/java/lang/TAbstractStringBuilder.java
@@ -15,12 +15,13 @@
  */
 package org.teavm.classlib.java.lang;
 
+import java.util.Arrays;
 import org.teavm.classlib.impl.text.DoubleAnalyzer;
 import org.teavm.classlib.impl.text.FloatAnalyzer;
 import org.teavm.classlib.java.io.TSerializable;
 import org.teavm.classlib.java.util.TArrays;
 
-class TAbstractStringBuilder extends TObject implements TSerializable, TCharSequence {
+class TAbstractStringBuilder implements TSerializable, TCharSequence {
     static class Constants {
         static int[] intPowersOfTen = { 1, 10, 100, 1000, 10000, 100000, 1000000, 10000000, 100000000,
                 1000000000 };
@@ -44,11 +45,11 @@ class TAbstractStringBuilder extends TObject implements TSerializable, TCharSequ
         buffer = new char[capacity];
     }
 
-    public TAbstractStringBuilder(TString value) {
-        this((TCharSequence) value);
+    public TAbstractStringBuilder(String value) {
+        this((CharSequence) value);
     }
 
-    public TAbstractStringBuilder(TCharSequence value) {
+    public TAbstractStringBuilder(CharSequence value) {
         buffer = new char[value.length()];
         for (int i = 0; i < buffer.length; ++i) {
             buffer[i] = value.charAt(i);
@@ -110,15 +111,15 @@ class TAbstractStringBuilder extends TObject implements TSerializable, TCharSequ
             } else {
                 insertSpace(target, target + 1);
             }
-            buffer[target++] = TCharacter.forDigit(value, radix);
+            buffer[target++] = Character.forDigit(value, radix);
         } else {
             int pos = 1;
             int sz = 1;
-            var posLimit = Integer.divideUnsigned(Integer.MAX_VALUE, radix);
+            var posLimit = Integer.divideUnsigned(-1, radix);
             while (Integer.compareUnsigned(pos * radix, value) <= 0) {
                 pos *= radix;
                 ++sz;
-                if (Integer.compareUnsigned(pos, posLimit) >= 0) {
+                if (Integer.compareUnsigned(pos, posLimit) > 0) {
                     break;
                 }
             }
@@ -129,8 +130,8 @@ class TAbstractStringBuilder extends TObject implements TSerializable, TCharSequ
             if (!positive) {
                 buffer[target++] = '-';
             }
-            while (pos > 0) {
-                buffer[target++] = TCharacter.forDigit(Integer.divideUnsigned(value, pos), radix);
+            while (pos != 0) {
+                buffer[target++] = Character.forDigit(Integer.divideUnsigned(value, pos), radix);
                 value = Integer.remainderUnsigned(value, pos);
                 pos = Integer.divideUnsigned(pos, radix);
             }
@@ -163,7 +164,7 @@ class TAbstractStringBuilder extends TObject implements TSerializable, TCharSequ
         } else {
             int sz = 1;
             long pos = 1;
-            var posLimit = Long.divideUnsigned(Long.MAX_VALUE, radix);
+            var posLimit = Long.divideUnsigned(-1, radix);
             while (Long.compareUnsigned(pos * radix, value) <= 0) {
                 pos *= radix;
                 ++sz;
@@ -178,7 +179,7 @@ class TAbstractStringBuilder extends TObject implements TSerializable, TCharSequ
             if (!positive) {
                 buffer[target++] = '-';
             }
-            while (pos > 0) {
+            while (pos != 0) {
                 buffer[target++] = TCharacter.forDigit((int) Long.divideUnsigned(value, pos), radix);
                 value = Long.remainderUnsigned(value, pos);
                 pos = Long.divideUnsigned(pos, radix);
@@ -527,7 +528,7 @@ class TAbstractStringBuilder extends TObject implements TSerializable, TCharSequ
         int newLength = buffer.length < Integer.MAX_VALUE / 2
                 ? Math.max(capacity, Math.max(buffer.length * 2, 5))
                 : Integer.MAX_VALUE;
-        buffer = TArrays.copyOf(buffer, newLength);
+        buffer = Arrays.copyOf(buffer, newLength);
     }
 
     public void trimToSize() {
diff --git a/classlib/src/main/java/org/teavm/classlib/java/lang/TStringBuffer.java b/classlib/src/main/java/org/teavm/classlib/java/lang/TStringBuffer.java
index 5dfe1173b..6d86a941b 100644
--- a/classlib/src/main/java/org/teavm/classlib/java/lang/TStringBuffer.java
+++ b/classlib/src/main/java/org/teavm/classlib/java/lang/TStringBuffer.java
@@ -24,11 +24,11 @@ public class TStringBuffer extends TAbstractStringBuilder implements TAppendable
         super();
     }
 
-    public TStringBuffer(TString value) {
+    public TStringBuffer(String value) {
         super(value);
     }
 
-    public TStringBuffer(TCharSequence value) {
+    public TStringBuffer(CharSequence value) {
         super(value);
     }
 
diff --git a/classlib/src/main/java/org/teavm/classlib/java/lang/TStringBuilder.java b/classlib/src/main/java/org/teavm/classlib/java/lang/TStringBuilder.java
index 689fe6388..765337902 100644
--- a/classlib/src/main/java/org/teavm/classlib/java/lang/TStringBuilder.java
+++ b/classlib/src/main/java/org/teavm/classlib/java/lang/TStringBuilder.java
@@ -24,11 +24,11 @@ public class TStringBuilder extends TAbstractStringBuilder implements TAppendabl
         super();
     }
 
-    public TStringBuilder(TString value) {
+    public TStringBuilder(String value) {
         super(value);
     }
 
-    public TStringBuilder(TCharSequence value) {
+    public TStringBuilder(CharSequence value) {
         super(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 7d108f249..09a19b4f4 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
@@ -178,7 +178,6 @@ public class IntegerTest {
         assertEquals("11110001001000000", Integer.toString(123456, 2));
         assertEquals("-10111", Integer.toString(-23, 2));
         assertEquals("1111111111111111111111111111111", Integer.toString(Integer.MAX_VALUE, 2));
-        // TODO: looks like there's a bug in compiler. Fix and uncomment
-        //assertEquals("-10000000000000000000000000000000", Integer.toString(Integer.MIN_VALUE, 2));
+        assertEquals("-10000000000000000000000000000000", Integer.toString(Integer.MIN_VALUE, 2));
     }
 }
diff --git a/tests/src/test/java/org/teavm/classlib/java/lang/LongTest.java b/tests/src/test/java/org/teavm/classlib/java/lang/LongTest.java
index 88a87abc5..4b0f35fbe 100644
--- a/tests/src/test/java/org/teavm/classlib/java/lang/LongTest.java
+++ b/tests/src/test/java/org/teavm/classlib/java/lang/LongTest.java
@@ -82,8 +82,7 @@ public class LongTest {
         assertEquals("-10111", Long.toString(-23, 2));
         assertEquals("111111111111111111111111111111111111111111111111111111111111111",
                 Long.toString(Long.MAX_VALUE, 2));
-        // TODO: looks like there's a bug in compiler. Fix and uncomment
-        /*assertEquals("-1000000000000000000000000000000000000000000000000000000000000000",
-                Long.toString(Long.MIN_VALUE, 2));*/
+        assertEquals("-1000000000000000000000000000000000000000000000000000000000000000",
+                Long.toString(Long.MIN_VALUE, 2));
     }
 }