diff --git a/core/src/main/java/org/teavm/backend/javascript/JavaScriptTarget.java b/core/src/main/java/org/teavm/backend/javascript/JavaScriptTarget.java
index 521f4c177..c9c183601 100644
--- a/core/src/main/java/org/teavm/backend/javascript/JavaScriptTarget.java
+++ b/core/src/main/java/org/teavm/backend/javascript/JavaScriptTarget.java
@@ -198,8 +198,9 @@ public class JavaScriptTarget implements TeaVMTarget, TeaVMJavaScriptHost {
     }
 
     @Override
-    public void emit(ListableClassHolderSource classes, OutputStream output, BuildTarget target) {
-        try (Writer writer = new OutputStreamWriter(output, "UTF-8")) {
+    public void emit(ListableClassHolderSource classes, BuildTarget target, String outputName) {
+        try (OutputStream output = target.createResource(outputName);
+                Writer writer = new OutputStreamWriter(output, "UTF-8")) {
             emit(classes, writer, target);
         } catch (IOException e) {
             throw new RenderingException(e);
diff --git a/core/src/main/java/org/teavm/backend/wasm/WasmTarget.java b/core/src/main/java/org/teavm/backend/wasm/WasmTarget.java
index 3676b8161..3cc17cc78 100644
--- a/core/src/main/java/org/teavm/backend/wasm/WasmTarget.java
+++ b/core/src/main/java/org/teavm/backend/wasm/WasmTarget.java
@@ -17,6 +17,8 @@ package org.teavm.backend.wasm;
 
 import java.io.IOException;
 import java.io.OutputStream;
+import java.io.OutputStreamWriter;
+import java.io.Writer;
 import java.util.ArrayList;
 import java.util.Arrays;
 import java.util.Collections;
@@ -66,6 +68,8 @@ import org.teavm.backend.wasm.model.expression.WasmStoreInt32;
 import org.teavm.backend.wasm.patches.ClassPatch;
 import org.teavm.backend.wasm.render.WasmBinaryRenderer;
 import org.teavm.backend.wasm.render.WasmBinaryWriter;
+import org.teavm.backend.wasm.render.WasmCRenderer;
+import org.teavm.backend.wasm.render.WasmRenderer;
 import org.teavm.dependency.ClassDependency;
 import org.teavm.dependency.DependencyChecker;
 import org.teavm.dependency.DependencyListener;
@@ -110,6 +114,8 @@ import org.teavm.vm.spi.TeaVMHostExtension;
 public class WasmTarget implements TeaVMTarget {
     private TeaVMTargetController controller;
     private boolean debugging;
+    private boolean wastEmitted;
+    private boolean cEmitted;
 
     @Override
     public void setController(TeaVMTargetController controller) {
@@ -149,6 +155,22 @@ public class WasmTarget implements TeaVMTarget {
         this.debugging = debugging;
     }
 
+    public boolean isWastEmitted() {
+        return wastEmitted;
+    }
+
+    public void setWastEmitted(boolean wastEmitted) {
+        this.wastEmitted = wastEmitted;
+    }
+
+    public boolean isCEmitted() {
+        return cEmitted;
+    }
+
+    public void setCEmitted(boolean cEmitted) {
+        this.cEmitted = cEmitted;
+    }
+
     @Override
     public void contributeDependencies(DependencyChecker dependencyChecker) {
         for (Class type : Arrays.asList(int.class, long.class, float.class, double.class)) {
@@ -189,7 +211,8 @@ public class WasmTarget implements TeaVMTarget {
     }
 
     @Override
-    public void emit(ListableClassHolderSource classes, OutputStream output, BuildTarget buildTarget) {
+    public void emit(ListableClassHolderSource classes, BuildTarget buildTarget, String outputName)
+            throws IOException {
         WasmModule module = new WasmModule();
         WasmFunction initFunction = new WasmFunction("__start__");
 
@@ -263,11 +286,41 @@ public class WasmTarget implements TeaVMTarget {
         WasmBinaryRenderer renderer = new WasmBinaryRenderer(writer);
         renderer.render(module);
 
-        try {
+        try (OutputStream output = buildTarget.createResource(outputName)) {
             output.write(writer.getData());
             output.flush();
-        } catch (IOException e) {
-            throw new RuntimeException(e);
+        }
+
+        if (wastEmitted) {
+            emitWast(module, buildTarget, getBaseName(outputName) + ".wast");
+        }
+        if (cEmitted) {
+            emitC(module, buildTarget, getBaseName(outputName) + ".c");
+        }
+    }
+
+    private String getBaseName(String name) {
+        int index = name.lastIndexOf('.');
+        return index < 0 ? name : name.substring(0, index);
+    }
+
+    private void emitWast(WasmModule module, BuildTarget buildTarget, String outputName) throws IOException {
+        WasmRenderer renderer = new WasmRenderer();
+        renderer.setLineNumbersEmitted(debugging);
+        renderer.render(module);
+        try (OutputStream output = buildTarget.createResource(outputName);
+                Writer writer = new OutputStreamWriter(output, "UTF-8")) {
+            writer.write(renderer.toString());
+        }
+    }
+
+    private void emitC(WasmModule module, BuildTarget buildTarget, String outputName) throws IOException {
+        WasmCRenderer renderer = new WasmCRenderer();
+        renderer.setLineNumbersEmitted(debugging);
+        renderer.render(module);
+        try (OutputStream output = buildTarget.createResource(outputName);
+                Writer writer = new OutputStreamWriter(output, "UTF-8")) {
+            writer.write(renderer.toString());
         }
     }
 
diff --git a/core/src/main/java/org/teavm/backend/wasm/render/CSingleLine.java b/core/src/main/java/org/teavm/backend/wasm/render/CSingleLine.java
index 1505d604e..c13ae2a75 100644
--- a/core/src/main/java/org/teavm/backend/wasm/render/CSingleLine.java
+++ b/core/src/main/java/org/teavm/backend/wasm/render/CSingleLine.java
@@ -45,7 +45,7 @@ class CSingleLine extends CLine {
 
     @Override
     void render(WasmCRenderer target) {
-        if (target.outputLineNumbers) {
+        if (target.lineNumbersEmitted) {
             TextLocation location = this.location;
             if (location == null) {
                 location = target.lastReportedLocation;
diff --git a/core/src/main/java/org/teavm/backend/wasm/render/WasmCRenderer.java b/core/src/main/java/org/teavm/backend/wasm/render/WasmCRenderer.java
index 22f99ee18..a56c1b8f1 100644
--- a/core/src/main/java/org/teavm/backend/wasm/render/WasmCRenderer.java
+++ b/core/src/main/java/org/teavm/backend/wasm/render/WasmCRenderer.java
@@ -29,15 +29,15 @@ public class WasmCRenderer {
     private int indentLevel;
     String currentFile = "";
     int currentLine = -1;
-    boolean outputLineNumbers;
+    boolean lineNumbersEmitted;
     TextLocation lastReportedLocation;
 
-    public boolean isOutputLineNumbers() {
-        return outputLineNumbers;
+    public boolean isLineNumbersEmitted() {
+        return lineNumbersEmitted;
     }
 
-    public void setOutputLineNumbers(boolean outputLineNumbers) {
-        this.outputLineNumbers = outputLineNumbers;
+    public void setLineNumbersEmitted(boolean value) {
+        this.lineNumbersEmitted = value;
     }
 
     void indent() {
diff --git a/core/src/main/java/org/teavm/backend/wasm/render/WasmRenderer.java b/core/src/main/java/org/teavm/backend/wasm/render/WasmRenderer.java
index 327ecdb28..e9453c089 100644
--- a/core/src/main/java/org/teavm/backend/wasm/render/WasmRenderer.java
+++ b/core/src/main/java/org/teavm/backend/wasm/render/WasmRenderer.java
@@ -45,6 +45,14 @@ public class WasmRenderer {
         return this;
     }
 
+    public boolean isLineNumbersEmitted() {
+        return visitor.lineNumbersEmitted;
+    }
+
+    public void setLineNumbersEmitted(boolean value) {
+        visitor.lineNumbersEmitted = value;
+    }
+
     public void render(WasmModule module) {
         visitor.open().append("module");
         renderMemory(module);
diff --git a/core/src/main/java/org/teavm/backend/wasm/render/WasmRenderingVisitor.java b/core/src/main/java/org/teavm/backend/wasm/render/WasmRenderingVisitor.java
index c27d250aa..e70e3ac79 100644
--- a/core/src/main/java/org/teavm/backend/wasm/render/WasmRenderingVisitor.java
+++ b/core/src/main/java/org/teavm/backend/wasm/render/WasmRenderingVisitor.java
@@ -67,6 +67,7 @@ class WasmRenderingVisitor implements WasmExpressionVisitor {
     private Map<WasmBlock, String> blockIdentifiers = new HashMap<>();
     private int indentLevel;
     private boolean lfDeferred;
+    boolean lineNumbersEmitted;
     List<WasmSignature> signatureList = new ArrayList<>();
     Map<WasmSignature, Integer> signatureMap = new HashMap<>();
 
@@ -97,7 +98,7 @@ class WasmRenderingVisitor implements WasmExpressionVisitor {
     }
 
     WasmRenderingVisitor line(WasmExpression expression) {
-        if (expression.getLocation() != null) {
+        if (expression.getLocation() != null && lineNumbersEmitted) {
             lf().append(";; " + expression.getLocation().getFileName() + ":" + expression.getLocation().getLine());
         }
         lf().append(expression);
diff --git a/core/src/main/java/org/teavm/vm/DirectoryBuildTarget.java b/core/src/main/java/org/teavm/vm/DirectoryBuildTarget.java
index d9b902d15..4f9cc9f57 100644
--- a/core/src/main/java/org/teavm/vm/DirectoryBuildTarget.java
+++ b/core/src/main/java/org/teavm/vm/DirectoryBuildTarget.java
@@ -15,15 +15,12 @@
  */
 package org.teavm.vm;
 
+import java.io.BufferedOutputStream;
 import java.io.File;
 import java.io.FileOutputStream;
 import java.io.IOException;
 import java.io.OutputStream;
 
-/**
- *
- * @author Alexey Andreev
- */
 public class DirectoryBuildTarget implements BuildTarget {
     private File directory;
 
@@ -40,6 +37,6 @@ public class DirectoryBuildTarget implements BuildTarget {
                 dir.mkdirs();
             }
         }
-        return new FileOutputStream(new File(directory, fileName));
+        return new BufferedOutputStream(new FileOutputStream(new File(directory, fileName)), 65536);
     }
 }
diff --git a/core/src/main/java/org/teavm/vm/TeaVM.java b/core/src/main/java/org/teavm/vm/TeaVM.java
index 62b9d3235..15bc01776 100644
--- a/core/src/main/java/org/teavm/vm/TeaVM.java
+++ b/core/src/main/java/org/teavm/vm/TeaVM.java
@@ -16,10 +16,7 @@
 package org.teavm.vm;
 
 import java.io.File;
-import java.io.FileOutputStream;
 import java.io.IOException;
-import java.io.OutputStream;
-import java.io.UnsupportedEncodingException;
 import java.util.ArrayList;
 import java.util.Arrays;
 import java.util.Collection;
@@ -329,11 +326,11 @@ public class TeaVM implements TeaVMHost, ServiceRepository {
      * actual generation happens and no exceptions thrown, but you can further call
      * {@link #getProblemProvider()} to learn the build state.</p>
      *
-     * @param output where to generate JavaScript. Should not be null.
      * @param buildTarget where to generate additional resources. Can be null, but if there are
-     * plugins or inteceptors that generate additional resources, the build process will fail.
+     * plugins or interceptors that generate additional resources, the build process will fail.
+     * @param outputName name of output file within buildTarget. Should not be null.
      */
-    public void build(OutputStream output, BuildTarget buildTarget) {
+    public void build(BuildTarget buildTarget, String outputName) {
         target.setController(targetController);
 
         // Check dependencies
@@ -381,7 +378,11 @@ public class TeaVM implements TeaVMHost, ServiceRepository {
         }
 
         // Render
-        target.emit(classSet, output, buildTarget);
+        try {
+            target.emit(classSet, buildTarget, outputName);
+        } catch (IOException e) {
+            throw new RuntimeException("Error generating output files", e);
+        }
     }
 
     @SuppressWarnings("WeakerAccess")
@@ -513,13 +514,7 @@ public class TeaVM implements TeaVMHost, ServiceRepository {
     }
 
     public void build(File dir, String fileName) {
-        try (OutputStream output = new FileOutputStream(new File(dir, fileName))) {
-            build(output, new DirectoryBuildTarget(dir));
-        } catch (UnsupportedEncodingException e) {
-            throw new RuntimeException("Platform does not support UTF-8", e);
-        } catch (IOException e) {
-            throw new RenderingException("IO error occurred", e);
-        }
+        build(new DirectoryBuildTarget(dir), fileName);
     }
 
     /**
diff --git a/core/src/main/java/org/teavm/vm/TeaVMTarget.java b/core/src/main/java/org/teavm/vm/TeaVMTarget.java
index 28253d79e..04df7b096 100644
--- a/core/src/main/java/org/teavm/vm/TeaVMTarget.java
+++ b/core/src/main/java/org/teavm/vm/TeaVMTarget.java
@@ -15,7 +15,7 @@
  */
 package org.teavm.vm;
 
-import java.io.OutputStream;
+import java.io.IOException;
 import java.util.List;
 import org.teavm.dependency.DependencyChecker;
 import org.teavm.dependency.DependencyListener;
@@ -36,5 +36,5 @@ public interface TeaVMTarget {
 
     void contributeDependencies(DependencyChecker dependencyChecker);
 
-    void emit(ListableClassHolderSource classes, OutputStream output, BuildTarget buildTarget);
+    void emit(ListableClassHolderSource classes, BuildTarget buildTarget, String outputName) throws IOException;
 }
diff --git a/tests/src/test/java/org/teavm/dependency/ClassValueTest.java b/tests/src/test/java/org/teavm/dependency/ClassValueTest.java
index fc956f1e8..e4e84c477 100644
--- a/tests/src/test/java/org/teavm/dependency/ClassValueTest.java
+++ b/tests/src/test/java/org/teavm/dependency/ClassValueTest.java
@@ -78,7 +78,7 @@ public class ClassValueTest {
         TeaVM vm = new TeaVMBuilder(new JavaScriptTarget()).build();
         vm.installPlugins();
         vm.entryPoint(new MethodReference(getClass().getName(), methodName, ValueType.VOID));
-        vm.build(new ByteArrayOutputStream(), null);
+        vm.build(fileName -> new ByteArrayOutputStream(), "tmp");
         if (!vm.getProblemProvider().getSevereProblems().isEmpty()) {
             fail("Code compiled with errors:\n" + describeProblems(vm));
         }
diff --git a/tests/src/test/java/org/teavm/tests/JSOTest.java b/tests/src/test/java/org/teavm/tests/JSOTest.java
index f4fd609ec..277310b8e 100644
--- a/tests/src/test/java/org/teavm/tests/JSOTest.java
+++ b/tests/src/test/java/org/teavm/tests/JSOTest.java
@@ -99,7 +99,7 @@ public class JSOTest {
         TeaVM vm = new TeaVMBuilder(new JavaScriptTarget()).build();
         vm.installPlugins();
         vm.entryPoint("org/teavm/metaprogramming/test", new MethodReference(JSOTest.class, methodName, void.class));
-        vm.build(new ByteArrayOutputStream(), null);
+        vm.build(name -> new ByteArrayOutputStream(), "tmp");
         return vm.getProblemProvider().getSevereProblems();
     }
 }
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 e7a3c7241..491c10721 100644
--- a/tools/core/src/main/java/org/teavm/tooling/TeaVMTool.java
+++ b/tools/core/src/main/java/org/teavm/tooling/TeaVMTool.java
@@ -15,7 +15,6 @@
  */
 package org.teavm.tooling;
 
-import java.io.BufferedOutputStream;
 import java.io.File;
 import java.io.FileOutputStream;
 import java.io.IOException;
@@ -406,44 +405,46 @@ public class TeaVMTool implements BaseTeaVMTool {
                 }
             }
             targetDirectory.mkdirs();
-            try (OutputStream output = new BufferedOutputStream(
-                    new FileOutputStream(new File(targetDirectory, getResolvedTargetFileName())), 65536)) {
-                Writer writer = new OutputStreamWriter(output, "UTF-8");
-                if (runtime == RuntimeCopyOperation.MERGED) {
-                    javaScriptTarget.add(runtimeInjector);
-                }
-                vm.build(output, new DirectoryBuildTarget(targetDirectory));
-                if (vm.wasCancelled()) {
-                    log.info("Build cancelled");
-                    cancelled = true;
-                    return;
-                }
 
-                ProblemProvider problemProvider = vm.getProblemProvider();
-                if (problemProvider.getProblems().isEmpty()) {
-                    log.info("Output file successfully built");
-                } else if (problemProvider.getSevereProblems().isEmpty()) {
-                    log.info("Output file built with warnings");
-                    TeaVMProblemRenderer.describeProblems(vm, log);
-                } else {
-                    log.info("Output file built with errors");
-                    TeaVMProblemRenderer.describeProblems(vm, log);
-                }
+            if (runtime == RuntimeCopyOperation.MERGED) {
+                javaScriptTarget.add(runtimeInjector);
+            }
+            BuildTarget buildTarget = new DirectoryBuildTarget(targetDirectory);
+            String outputName = getResolvedTargetFileName();
+            vm.build(buildTarget, outputName);
+            if (vm.wasCancelled()) {
+                log.info("Build cancelled");
+                cancelled = true;
+                return;
+            }
 
-                if (targetType == TeaVMTargetType.JAVASCRIPT) {
+            ProblemProvider problemProvider = vm.getProblemProvider();
+            if (problemProvider.getProblems().isEmpty()) {
+                log.info("Output file successfully built");
+            } else if (problemProvider.getSevereProblems().isEmpty()) {
+                log.info("Output file built with warnings");
+                TeaVMProblemRenderer.describeProblems(vm, log);
+            } else {
+                log.info("Output file built with errors");
+                TeaVMProblemRenderer.describeProblems(vm, log);
+            }
+
+            if (targetType == TeaVMTargetType.JAVASCRIPT) {
+                try (OutputStream output = buildTarget.createResource(outputName)) {
+                    Writer writer = new OutputStreamWriter(output, "UTF-8");
                     additionalJavaScriptOutput(writer);
                 }
+            }
 
-                if (incremental) {
-                    programCache.flush();
-                    if (astCache != null) {
-                        astCache.flush();
-                    }
-                    cachedClassSource.flush();
-                    symbolTable.flush();
-                    fileTable.flush();
-                    log.info("Cache updated");
+            if (incremental) {
+                programCache.flush();
+                if (astCache != null) {
+                    astCache.flush();
                 }
+                cachedClassSource.flush();
+                symbolTable.flush();
+                fileTable.flush();
+                log.info("Cache updated");
             }
         } catch (IOException e) {
             throw new TeaVMToolException("IO error occurred", e);
diff --git a/tools/junit/src/main/java/org/teavm/junit/TeaVMTestRunner.java b/tools/junit/src/main/java/org/teavm/junit/TeaVMTestRunner.java
index 656225218..acb8f5e8b 100644
--- a/tools/junit/src/main/java/org/teavm/junit/TeaVMTestRunner.java
+++ b/tools/junit/src/main/java/org/teavm/junit/TeaVMTestRunner.java
@@ -360,16 +360,14 @@ public class TeaVMTestRunner extends Runner {
         applyProperties(method.getDeclaringClass(), properties);
         vm.setProperties(properties);
 
-        try (OutputStream innerWriter = new FileOutputStream(outputFile)) {
-            MethodReference exceptionMsg = new MethodReference(ExceptionHelper.class, "showException",
-                    Throwable.class, String.class);
-            vm.entryPoint("runTest", new MethodReference(TestEntryPoint.class, "run", void.class)).async();
-            vm.entryPoint("extractException", exceptionMsg);
-            vm.build(innerWriter, new DirectoryBuildTarget(outputDir));
-            if (!vm.getProblemProvider().getProblems().isEmpty()) {
-                result.success = false;
-                result.errorMessage = buildErrorMessage(vm);
-            }
+        MethodReference exceptionMsg = new MethodReference(ExceptionHelper.class, "showException",
+                Throwable.class, String.class);
+        vm.entryPoint("runTest", new MethodReference(TestEntryPoint.class, "run", void.class)).async();
+        vm.entryPoint("extractException", exceptionMsg);
+        vm.build(new DirectoryBuildTarget(outputFile.getParentFile()), outputFile.getName());
+        if (!vm.getProblemProvider().getProblems().isEmpty()) {
+            result.success = false;
+            result.errorMessage = buildErrorMessage(vm);
         }
 
         return result;