diff --git a/classlib/src/main/java/org/teavm/classlib/impl/currency/CountriesGenerator.java b/classlib/src/main/java/org/teavm/classlib/impl/currency/CountriesGenerator.java
index dcb712422..522c8cae1 100644
--- a/classlib/src/main/java/org/teavm/classlib/impl/currency/CountriesGenerator.java
+++ b/classlib/src/main/java/org/teavm/classlib/impl/currency/CountriesGenerator.java
@@ -15,6 +15,7 @@
  */
 package org.teavm.classlib.impl.currency;
 
+import java.io.BufferedInputStream;
 import java.io.BufferedReader;
 import java.io.IOException;
 import java.io.InputStream;
@@ -24,15 +25,11 @@ import java.util.List;
 import org.teavm.model.MethodReference;
 import org.teavm.platform.metadata.*;
 
-/**
- *
- * @author Alexey Andreev
- */
 public class CountriesGenerator implements MetadataGenerator {
     @Override
     public Resource generateMetadata(MetadataGeneratorContext context, MethodReference method) {
-        try (InputStream input = context.getClassLoader().getResourceAsStream(
-                "org/teavm/classlib/impl/currency/iso3166.csv")) {
+        try (InputStream input = new BufferedInputStream(context.getClassLoader().getResourceAsStream(
+                "org/teavm/classlib/impl/currency/iso3166.csv"))) {
             if (input == null) {
                 throw new AssertionError("ISO 3166 table was not found");
             }
diff --git a/classlib/src/main/java/org/teavm/classlib/impl/currency/CurrenciesGenerator.java b/classlib/src/main/java/org/teavm/classlib/impl/currency/CurrenciesGenerator.java
index f399d7181..e03c4fb62 100644
--- a/classlib/src/main/java/org/teavm/classlib/impl/currency/CurrenciesGenerator.java
+++ b/classlib/src/main/java/org/teavm/classlib/impl/currency/CurrenciesGenerator.java
@@ -15,6 +15,7 @@
  */
 package org.teavm.classlib.impl.currency;
 
+import java.io.BufferedInputStream;
 import java.io.IOException;
 import java.io.InputStream;
 import java.util.Iterator;
@@ -29,10 +30,6 @@ import org.teavm.platform.metadata.ResourceArray;
 import org.w3c.dom.*;
 import org.xml.sax.SAXException;
 
-/**
- *
- * @author Alexey Andreev
- */
 public class CurrenciesGenerator implements MetadataGenerator {
     @Override
     public Resource generateMetadata(MetadataGeneratorContext context, MethodReference method) {
@@ -41,7 +38,7 @@ public class CurrenciesGenerator implements MetadataGenerator {
                 "org/teavm/classlib/impl/currency/iso4217.xml")) {
             DocumentBuilderFactory builderFactory = DocumentBuilderFactory.newInstance();
             DocumentBuilder builder = builderFactory.newDocumentBuilder();
-            doc = builder.parse(input);
+            doc = builder.parse(new BufferedInputStream(input));
         } catch (IOException | ParserConfigurationException | SAXException e) {
             throw new RuntimeException("Error reading ISO 4217 medata from file");
         }
diff --git a/classlib/src/main/java/org/teavm/classlib/impl/tz/TimeZoneGenerator.java b/classlib/src/main/java/org/teavm/classlib/impl/tz/TimeZoneGenerator.java
index 86e4d0d66..416b42184 100644
--- a/classlib/src/main/java/org/teavm/classlib/impl/tz/TimeZoneGenerator.java
+++ b/classlib/src/main/java/org/teavm/classlib/impl/tz/TimeZoneGenerator.java
@@ -15,6 +15,7 @@
  */
 package org.teavm.classlib.impl.tz;
 
+import java.io.BufferedInputStream;
 import java.io.BufferedReader;
 import java.io.IOException;
 import java.io.InputStream;
@@ -27,17 +28,13 @@ import org.teavm.platform.metadata.MetadataGenerator;
 import org.teavm.platform.metadata.MetadataGeneratorContext;
 import org.teavm.platform.metadata.ResourceMap;
 
-/**
- *
- * @author Alexey Andreev
- */
 public class TimeZoneGenerator implements MetadataGenerator {
     public static final String TIMEZONE_DB_VERSION = "2015d";
     public static final String TIMEZONE_DB_PATH = "org/teavm/classlib/impl/tz/tzdata" + TIMEZONE_DB_VERSION + ".zip";
 
     public static void compile(ZoneInfoCompiler compiler, ClassLoader classLoader) {
         try (InputStream input = classLoader.getResourceAsStream(TIMEZONE_DB_PATH)) {
-            try (ZipInputStream zip = new ZipInputStream(input)) {
+            try (ZipInputStream zip = new ZipInputStream(new BufferedInputStream(input))) {
                 while (true) {
                     ZipEntry entry = zip.getNextEntry();
                     if (entry == null) {
@@ -76,7 +73,7 @@ public class TimeZoneGenerator implements MetadataGenerator {
         try (InputStream input = context.getClassLoader().getResourceAsStream("org/teavm/classlib/impl/tz/cache")) {
             if (input != null) {
                 TimeZoneCache cache = new TimeZoneCache();
-                zones = cache.read(input).values();
+                zones = cache.read(new BufferedInputStream(input)).values();
             } else {
                 compile(compiler, context.getClassLoader());
                 zones = compiler.compile().values();
diff --git a/classlib/src/main/java/org/teavm/classlib/impl/unicode/CLDRReader.java b/classlib/src/main/java/org/teavm/classlib/impl/unicode/CLDRReader.java
index 9c453341e..daa58847b 100644
--- a/classlib/src/main/java/org/teavm/classlib/impl/unicode/CLDRReader.java
+++ b/classlib/src/main/java/org/teavm/classlib/impl/unicode/CLDRReader.java
@@ -18,6 +18,7 @@ package org.teavm.classlib.impl.unicode;
 import com.google.gson.JsonElement;
 import com.google.gson.JsonObject;
 import com.google.gson.JsonParser;
+import java.io.BufferedInputStream;
 import java.io.IOException;
 import java.io.InputStream;
 import java.io.InputStreamReader;
@@ -33,10 +34,6 @@ import java.util.Set;
 import java.util.zip.ZipEntry;
 import java.util.zip.ZipInputStream;
 
-/**
- *
- * @author Alexey Andreev
- */
 public class CLDRReader {
     private static String[] weekdayKeys = { "sun", "mon", "tue", "wed", "thu", "fri", "sat" };
     private Map<String, CLDRLocale> knownLocales = new LinkedHashMap<>();
@@ -82,8 +79,8 @@ public class CLDRReader {
     }
 
     private void readCLDR(ClassLoader classLoader) {
-        try (ZipInputStream input = new ZipInputStream(classLoader.getResourceAsStream(
-                "org/teavm/classlib/impl/unicode/cldr-json.zip"))) {
+        try (ZipInputStream input = new ZipInputStream(new BufferedInputStream(classLoader.getResourceAsStream(
+                "org/teavm/classlib/impl/unicode/cldr-json.zip")))) {
             while (true) {
                 ZipEntry entry = input.getNextEntry();
                 if (entry == null) {
diff --git a/classlib/src/main/java/org/teavm/classlib/java/lang/ClassLoaderNativeGenerator.java b/classlib/src/main/java/org/teavm/classlib/java/lang/ClassLoaderNativeGenerator.java
index ba5cf5f0e..b2c10caa4 100644
--- a/classlib/src/main/java/org/teavm/classlib/java/lang/ClassLoaderNativeGenerator.java
+++ b/classlib/src/main/java/org/teavm/classlib/java/lang/ClassLoaderNativeGenerator.java
@@ -15,6 +15,7 @@
  */
 package org.teavm.classlib.java.lang;
 
+import java.io.BufferedInputStream;
 import java.io.IOException;
 import java.io.InputStream;
 import java.util.Arrays;
@@ -68,7 +69,7 @@ public class ClassLoaderNativeGenerator implements Injector {
                 }
                 first = false;
                 writer.newLine();
-                String data = Base64.getEncoder().encodeToString(IOUtils.toByteArray(input));
+                String data = Base64.getEncoder().encodeToString(IOUtils.toByteArray(new BufferedInputStream(input)));
                 writer.append("\"").append(RenderingUtil.escapeString(resource)).append("\"");
                 writer.ws().append(':').ws();
                 writer.append("\"").append(data).append("\"");
diff --git a/core/src/main/java/org/teavm/model/ClassHolderSource.java b/core/src/main/java/org/teavm/model/ClassHolderSource.java
index 8274a3c1e..15c079c2b 100644
--- a/core/src/main/java/org/teavm/model/ClassHolderSource.java
+++ b/core/src/main/java/org/teavm/model/ClassHolderSource.java
@@ -17,10 +17,6 @@ package org.teavm.model;
 
 import java.util.stream.Stream;
 
-/**
- *
- * @author Alexey Andreev
- */
 public interface ClassHolderSource extends ClassReaderSource {
     @Override
     ClassHolder get(String name);
diff --git a/core/src/main/java/org/teavm/parsing/ClasspathResourceProvider.java b/core/src/main/java/org/teavm/parsing/ClasspathResourceProvider.java
index b8b5f6d1a..480c07b41 100644
--- a/core/src/main/java/org/teavm/parsing/ClasspathResourceProvider.java
+++ b/core/src/main/java/org/teavm/parsing/ClasspathResourceProvider.java
@@ -15,12 +15,9 @@
  */
 package org.teavm.parsing;
 
+import java.io.BufferedInputStream;
 import java.io.InputStream;
 
-/**
- *
- * @author Alexey Andreev
- */
 public class ClasspathResourceProvider implements ResourceProvider {
     private ClassLoader classLoader;
 
@@ -35,6 +32,7 @@ public class ClasspathResourceProvider implements ResourceProvider {
 
     @Override
     public InputStream openResource(String name) {
-        return classLoader.getResourceAsStream(name);
+        InputStream result = classLoader.getResourceAsStream(name);
+        return result != null ? new BufferedInputStream(result) : null;
     }
 }
diff --git a/core/src/main/java/org/teavm/parsing/resource/ClasspathResourceReader.java b/core/src/main/java/org/teavm/parsing/resource/ClasspathResourceReader.java
index ba20ffa45..4c065f275 100644
--- a/core/src/main/java/org/teavm/parsing/resource/ClasspathResourceReader.java
+++ b/core/src/main/java/org/teavm/parsing/resource/ClasspathResourceReader.java
@@ -15,13 +15,10 @@
  */
 package org.teavm.parsing.resource;
 
+import java.io.BufferedInputStream;
 import java.io.IOException;
 import java.io.InputStream;
 
-/**
- *
- * @author Alexey Andreev
- */
 public class ClasspathResourceReader implements ResourceReader {
     private ClassLoader classLoader;
 
@@ -51,6 +48,7 @@ public class ClasspathResourceReader implements ResourceReader {
 
     @Override
     public InputStream openResource(String name) throws IOException {
-        return classLoader.getResourceAsStream(name);
+        InputStream result = classLoader.getResourceAsStream(name);
+        return result != null ? new BufferedInputStream(result) : null;
     }
 }
diff --git a/core/src/main/java/org/teavm/vm/TeaVMPluginLoader.java b/core/src/main/java/org/teavm/vm/TeaVMPluginLoader.java
index b4db270ed..16a9f5a1a 100644
--- a/core/src/main/java/org/teavm/vm/TeaVMPluginLoader.java
+++ b/core/src/main/java/org/teavm/vm/TeaVMPluginLoader.java
@@ -15,6 +15,7 @@
  */
 package org.teavm.vm;
 
+import java.io.BufferedInputStream;
 import java.io.BufferedReader;
 import java.io.IOException;
 import java.io.InputStream;
@@ -120,7 +121,7 @@ public final class TeaVMPluginLoader {
             if (input == null) {
                 return false;
             }
-            ClassReader reader = new ClassReader(input);
+            ClassReader reader = new ClassReader(new BufferedInputStream(input));
             PluginDescriptorFiller filler = new PluginDescriptorFiller(descriptor);
             reader.accept(filler, 0);
             return true;
diff --git a/metaprogramming/impl/src/main/java/org/teavm/metaprogramming/impl/MetaprogrammingClassLoader.java b/metaprogramming/impl/src/main/java/org/teavm/metaprogramming/impl/MetaprogrammingClassLoader.java
index 6b00fd20c..39162f340 100644
--- a/metaprogramming/impl/src/main/java/org/teavm/metaprogramming/impl/MetaprogrammingClassLoader.java
+++ b/metaprogramming/impl/src/main/java/org/teavm/metaprogramming/impl/MetaprogrammingClassLoader.java
@@ -15,6 +15,7 @@
  */
 package org.teavm.metaprogramming.impl;
 
+import java.io.BufferedInputStream;
 import java.io.IOException;
 import java.io.InputStream;
 import java.util.HashMap;
@@ -42,7 +43,7 @@ public class MetaprogrammingClassLoader extends ClassLoader {
             return super.loadClass(name, resolve);
         } else {
             try (InputStream input = getResourceAsStream(name.replace('.', '/') + ".class")) {
-                byte[] array = instrumentation.instrument(IOUtils.toByteArray(input));
+                byte[] array = instrumentation.instrument(IOUtils.toByteArray(new BufferedInputStream(input)));
                 return defineClass(name, array, 0, array.length);
             } catch (IOException e) {
                 throw new ClassNotFoundException("Error reading bytecode of class " + name, e);
@@ -84,7 +85,8 @@ public class MetaprogrammingClassLoader extends ClassLoader {
             if (input == null) {
                 return false;
             }
-            new ClassReader(input).accept(visitor, ClassReader.SKIP_CODE | ClassReader.SKIP_DEBUG);
+            new ClassReader(new BufferedInputStream(input))
+                    .accept(visitor, ClassReader.SKIP_CODE | ClassReader.SKIP_DEBUG);
         } catch (IOException e) {
             return false;
         }
@@ -109,7 +111,8 @@ public class MetaprogrammingClassLoader extends ClassLoader {
             if (input == null) {
                 return false;
             }
-            new ClassReader(input).accept(visitor, ClassReader.SKIP_CODE | ClassReader.SKIP_DEBUG);
+            new ClassReader(new BufferedInputStream(input))
+                    .accept(visitor, ClassReader.SKIP_CODE | ClassReader.SKIP_DEBUG);
         } catch (IOException e) {
             return false;
         }
diff --git a/tools/core/src/main/java/org/teavm/tooling/TeaVMTool.java b/tools/core/src/main/java/org/teavm/tooling/TeaVMTool.java
index 953b980cc..ed1dde646 100644
--- a/tools/core/src/main/java/org/teavm/tooling/TeaVMTool.java
+++ b/tools/core/src/main/java/org/teavm/tooling/TeaVMTool.java
@@ -15,6 +15,7 @@
  */
 package org.teavm.tooling;
 
+import java.io.BufferedInputStream;
 import java.io.BufferedOutputStream;
 import java.io.File;
 import java.io.FileOutputStream;
@@ -558,8 +559,8 @@ public class TeaVMTool implements BaseTeaVMTool {
     private void resourceToFile(String resource, String fileName) throws IOException {
         try (InputStream input = TeaVMTool.class.getClassLoader().getResourceAsStream(resource)) {
             File outputFile = new File(targetDirectory, fileName);
-            try (OutputStream output = new FileOutputStream(outputFile)) {
-                IOUtils.copy(input, output);
+            try (OutputStream output = new BufferedOutputStream(new FileOutputStream(outputFile))) {
+                IOUtils.copy(new BufferedInputStream(input), output);
             }
             generatedFiles.add(outputFile);
         }
@@ -567,7 +568,7 @@ public class TeaVMTool implements BaseTeaVMTool {
 
     private void resourceToWriter(String resource, Writer writer) throws IOException {
         try (InputStream input = TeaVMTool.class.getClassLoader().getResourceAsStream(resource)) {
-            IOUtils.copy(input, writer, "UTF-8");
+            IOUtils.copy(new BufferedInputStream(input), writer, "UTF-8");
         }
     }
 }
diff --git a/tools/idea/jps-plugin/src/main/java/org/teavm/idea/jps/RenamingClassLoader.java b/tools/idea/jps-plugin/src/main/java/org/teavm/idea/jps/RenamingClassLoader.java
index b4931fb49..484229829 100644
--- a/tools/idea/jps-plugin/src/main/java/org/teavm/idea/jps/RenamingClassLoader.java
+++ b/tools/idea/jps-plugin/src/main/java/org/teavm/idea/jps/RenamingClassLoader.java
@@ -15,6 +15,7 @@
  */
 package org.teavm.idea.jps;
 
+import java.io.BufferedInputStream;
 import java.io.IOException;
 import java.io.InputStream;
 import java.net.URL;
@@ -44,7 +45,7 @@ public class RenamingClassLoader extends URLClassLoader {
         }
 
         try (InputStream input = getResourceAsStream(name.replace('.', '/') + ".class")) {
-            ClassReader classReader = new ClassReader(input);
+            ClassReader classReader = new ClassReader(new BufferedInputStream(input));
             ClassWriter writer = new ClassWriter(0);
             RenamingVisitor visitor = new RenamingVisitor(writer);
             for (Rename rename : renameList) {