diff --git a/gulpfile.js b/gulpfile.js
index cb349583a..2a19ce5fc 100644
--- a/gulpfile.js
+++ b/gulpfile.js
@@ -86,11 +86,10 @@ gulp.task('test.e2e', ['test.compile'], function(done) {
 
 gulp.task('test', ['test.unit', 'test.e2e', 'test.check-format']);
 
-gulp.task('watch', ['test.unit', 'test.check-format'], function() {
+gulp.task('watch', function() {
   failOnError = false;
-  // Avoid watching generated .d.ts in the build (aka output) directory.
-  return gulp.watch(
-      ['src/**/*.ts', 'test/**/*.ts', 'test_files/**'], {ignoreInitial: true}, ['test.unit']);
+  gulp.start(['test.unit']);  // Trigger initial build.
+  return gulp.watch(['src/**/*.ts', 'test/**/*.ts', 'test_files/**'], ['test.unit']);
 });
 
 gulp.task('default', ['compile']);
diff --git a/package.json b/package.json
index 2e168c460..64c2353ba 100644
--- a/package.json
+++ b/package.json
@@ -13,7 +13,7 @@
   },
   "devDependencies": {
     "chai": "^2.1.1",
-    "clang-format": "^1.0.32",
+    "clang-format": "1.0.33",
     "closure-compiler": "^0.2.12",
     "gulp": "^3.8.11",
     "gulp-clang-format": "^1.0.22",
diff --git a/src/sickle.ts b/src/sickle.ts
index 5731b3391..18b463f0b 100644
--- a/src/sickle.ts
+++ b/src/sickle.ts
@@ -3,12 +3,12 @@ import * as ts from 'typescript';
 export function formatDiagnostics(diags: ts.Diagnostic[]): string {
   return diags.map((d) => {
                 let res = ts.DiagnosticCategory[d.category];
-                if (d.file) res += d.file + ':';
+                if (d.file) res += ' at ' + d.file.fileName + ':';
                 if (d.start) {
                   let {line, character} = d.file.getLineAndCharacterOfPosition(d.start);
                   res += line + ':' + character + ':';
                 }
-                res += d.messageText;
+                res += ' ' + d.messageText;
                 return res;
               })
       .join('\n');
@@ -20,6 +20,8 @@ export type StringMap = {
 
 export type AnnotatedProgram = StringMap;
 
+const VISIBILITY_FLAGS = ts.NodeFlags.Private | ts.NodeFlags.Protected | ts.NodeFlags.Public;
+
 /**
  * A source processor that takes TypeScript code and annotates the output with Closure-style JSDoc
  * comments.
@@ -51,6 +53,8 @@ class Annotator {
     return res;
   }
 
+  private emit(str: string) { this.output.push(str); }
+
   private visit(node: ts.Node) {
     // console.log('node:', (<any>ts).SyntaxKind[node.kind]);
     switch (node.kind) {
@@ -58,15 +62,58 @@ class Annotator {
         this.maybeVisitType((<ts.VariableDeclaration>node).type);
         this.writeNode(node);
         break;
+      case ts.SyntaxKind.ClassDeclaration: {
+        let classNode = <ts.ClassDeclaration>node;
+        let hasCtor = classNode.members.some((e) => e.kind === ts.SyntaxKind.Constructor);
+        if (hasCtor) {
+          this.writeNode(classNode);
+          break;
+        }
+        // Emit a synthetic ctor.
+        // TODO(martinprobst): Handle inherited parent ctors.
+        this.writeTextBetween(classNode, classNode.getLastToken());
+        this.emit('constructor() {\n');
+        this.emitStubDeclarations(classNode, []);
+        this.emit('}\n');
+        this.writeNode(classNode.getLastToken());
+        break;
+      }
+      case ts.SyntaxKind.Constructor: {
+        let ctor = <ts.ConstructorDeclaration>node;
+        this.writeTextBetween(ctor, ctor.body);
+        if (ctor.body.statements.length) {
+          // Insert before the first code in the ctor.
+          this.writeTextBetween(ctor.body, ctor.body.statements[0]);
+        } else {
+          // Empty ctor - just insert before the end of it.
+          this.writeTextBetween(ctor.body, ctor.body.getLastToken());
+        }
+
+        let paramProps = ctor.parameters.filter((p) => !!(p.flags & VISIBILITY_FLAGS));
+        this.emitStubDeclarations(<ts.ClassLikeDeclaration>ctor.parent, paramProps);
+
+        if (ctor.body.statements.length) {
+          let firstStmt = ctor.body.statements[0];
+          this.emit(
+              ctor.body.getSourceFile().getText().substring(
+                  firstStmt.getFullStart(), ctor.body.getEnd()));
+        } else {
+          let remaining = ctor.getSourceFile().getText().substring(
+              ctor.body.getLastToken().getFullStart(), ctor.body.getEnd());
+          this.emit(remaining);
+        }
+
+        break;
+      }
       case ts.SyntaxKind.FunctionDeclaration:
       case ts.SyntaxKind.ArrowFunction:
         let fnDecl = <ts.FunctionLikeDeclaration>node;
-        this.maybeVisitType(fnDecl.type, true);
+        this.maybeVisitType(fnDecl.type, '@return');
         let writeOffset = fnDecl.getFullStart();
         // Parameters.
         if (fnDecl.parameters.length) {
           for (let param of fnDecl.parameters) {
-            this.writeTextBetween(fnDecl, writeOffset, param);
+            this.writeTextFromOffset(writeOffset, param);
             writeOffset = param.getEnd();
             this.maybeVisitType(param.type);
             this.visit(param);
@@ -74,12 +121,12 @@ class Annotator {
         }
         // Return type.
         if (fnDecl.type) {
-          this.writeTextBetween(fnDecl, writeOffset, fnDecl.type);
+          this.writeTextFromOffset(writeOffset, fnDecl.type);
           this.visit(fnDecl.type);
           writeOffset = fnDecl.type.getEnd();
         }
         // Body.
-        this.writeTextBetween(fnDecl, writeOffset, fnDecl.body);
+        this.writeTextFromOffset(writeOffset, fnDecl.body);
         this.visit(fnDecl.body);
         break;
       default:
@@ -88,23 +135,44 @@ class Annotator {
     }
   }
 
-  private maybeVisitType(type: ts.TypeNode, isReturn?: boolean) {
+  private emitStubDeclarations(
+      classDecl: ts.ClassLikeDeclaration, paramProps: ts.ParameterDeclaration[]) {
+    this.emit('\n\n// Sickle: begin stub declarations.\n');
+    this.emit('\n');
+    let props = <ts.PropertyDeclaration[]>(
+        classDecl.members.filter((e) => e.kind === ts.SyntaxKind.PropertyDeclaration));
+    props.forEach((p) => this.visitProperty(p));
+    paramProps.forEach((p) => this.visitProperty(p));
+    this.emit('// Sickle: end stub declarations.\n');
+  }
+
+  private visitProperty(p: ts.PropertyDeclaration | ts.ParameterDeclaration) {
+    this.maybeVisitType(p.type, '@type');
+    this.emit('\nthis.');
+    this.emit(p.name.getText());
+    this.emit(';');
+    this.emit('\n');
+  }
+
+  private maybeVisitType(type: ts.TypeNode, jsDocTag?: string) {
     if (!type) return;
-    this.output.push(' /**');
-    if (isReturn) {
-      this.output.push(' @return {');
+    this.emit(' /**');
+    if (jsDocTag) {
+      this.emit(' ');
+      this.emit(jsDocTag);
+      this.emit(' {');
     }
     this.visit(type);
-    if (isReturn) {
-      this.output.push('}');
+    if (jsDocTag) {
+      this.emit('}');
     }
-    this.output.push(' */');
+    this.emit(' */');
   }
 
-  private writeNode(node: ts.Node, upTo?: number) {
+  private writeNode(node: ts.Node) {
     if (node.getChildCount() == 0) {
       // Directly write complete tokens.
-      this.output.push(node.getFullText());
+      this.emit(node.getFullText());
       return;
     }
     let lastEnd = node.getFullStart();
@@ -114,17 +182,25 @@ class Annotator {
       this.visit(child);
       lastEnd = child.getEnd();
     }
+    // Write any trailing text.
+    let text = node.getSourceFile().getText().slice(lastEnd, node.getEnd());
+    if (text) this.emit(text);
+  }
+
+  private writeTextBetween(node: ts.Node, to: ts.Node) {
+    let text = node.getSourceFile().getText().slice(node.getFullStart(), to.getFullStart());
+    if (text) this.emit(text);
   }
 
-  private writeTextBetween(node: ts.Node, from: number, to: ts.Node) {
-    let text = node.getSourceFile().getText().slice(from, to.getFullStart());
-    this.output.push(text);
+  private writeTextFromOffset(from: number, to: ts.Node) {
+    let text = to.getSourceFile().getText().slice(from, to.getFullStart());
+    if (text) this.emit(text);
   }
 
   private writeSourceBefore(offset: number, node: ts.Node) {
     if (node.getFullStart() == offset) return;
     assert(node.getFullStart() > offset, 'Offset must not be smaller');
-    this.output.push(node.getSourceFile().getText().slice(offset, node.getFullStart()));
+    this.emit(node.getSourceFile().getText().slice(offset, node.getFullStart()));
   }
 
   private fail(msg: string) { throw new Error(msg); }
diff --git a/test/e2e_test.ts b/test/e2e_test.ts
index 547198ccc..8b812de50 100644
--- a/test/e2e_test.ts
+++ b/test/e2e_test.ts
@@ -16,7 +16,7 @@ export function checkClosureCompile(jsFiles: string[], done: (err: Error) => voi
     'checks-only': true,
     'jscomp_error': 'checkTypes',
     'js': jsFiles,
-    'language_in': 'ECMASCRIPT6'
+    'language_in': 'ECMASCRIPT6_STRICT'
   };
 
   compile(null, CLOSURE_COMPILER_OPTS, (err, stdout, stderr) => {
diff --git a/test/sickle_test.ts b/test/sickle_test.ts
index 87d50d758..d41287e3e 100644
--- a/test/sickle_test.ts
+++ b/test/sickle_test.ts
@@ -6,8 +6,16 @@ import {expect} from 'chai';
 import {annotateProgram, formatDiagnostics} from '../src/sickle';
 import {expectSource, goldenTests} from './test_support';
 
+let RUN_TESTS_MATCHING: RegExp = null;
+// RUN_TESTS_MATCHING = /fields/;
+
 describe('golden tests', () => {
+
   goldenTests().forEach((test) => {
+    if (RUN_TESTS_MATCHING && !RUN_TESTS_MATCHING.exec(test.name)) {
+      it.skip(test.name);
+      return;
+    }
     var tsSource = fs.readFileSync(test.tsPath, 'utf-8');
     var jsSource = fs.readFileSync(test.jsPath, 'utf-8');
     it(test.name, () => { expectSource(tsSource).to.equal(jsSource); });
diff --git a/test/test_support.ts b/test/test_support.ts
index c15ae98ca..fd54012fe 100644
--- a/test/test_support.ts
+++ b/test/test_support.ts
@@ -58,7 +58,8 @@ function transformSource(src: string): string {
 
   var program = ts.createProgram(['main.ts'], OPTIONS, host);
   if (program.getSyntacticDiagnostics().length) {
-    throw new Error(formatDiagnostics(ts.getPreEmitDiagnostics(program)));
+    throw new Error(
+        'Failed to parse ' + src + '\n' + formatDiagnostics(ts.getPreEmitDiagnostics(program)));
   }
 
   var transformed: StringMap = {};
@@ -73,7 +74,7 @@ function transformSource(src: string): string {
 
 export function expectSource(src: string) {
   var annotated = annotateSource(src);
-  // console.log('Annotated', annotated);
+  // console.log('Annotated:\n', annotated);
   var transformed = transformSource(annotated);
   return expect(transformed);
 }
diff --git a/test_files/fields.js b/test_files/fields.js
new file mode 100644
index 000000000..b7f033080
--- /dev/null
+++ b/test_files/fields.js
@@ -0,0 +1,18 @@
+class Klass {
+    constructor(field3) {
+        // Sickle: begin stub declarations.
+        this.field3 = field3;
+        /** @type { string} */
+        this.field1;
+        /** @type { number} */
+        this.field2;
+        /** @type { number} */
+        this.field3;
+        // Sickle: end stub declarations.
+        this.field3 = 2 + 1;
+    }
+    getF1() {
+        // This access print a warning without a generated field stub declaration.
+        return this.field1;
+    }
+}
diff --git a/test_files/fields.ts b/test_files/fields.ts
new file mode 100644
index 000000000..6082e14e3
--- /dev/null
+++ b/test_files/fields.ts
@@ -0,0 +1,13 @@
+class Klass {
+  field1: string;
+  field2: number;
+
+  constructor(private field3: number) {
+    this.field3 = 2 + 1;
+  }
+
+  getF1() {
+    // This access print a warning without a generated field stub declaration.
+    return this.field1;
+  }
+}
diff --git a/test_files/fields_no_ctor.js b/test_files/fields_no_ctor.js
new file mode 100644
index 000000000..e45a15eef
--- /dev/null
+++ b/test_files/fields_no_ctor.js
@@ -0,0 +1,8 @@
+class NoCtor {
+    constructor() {
+        // Sickle: begin stub declarations.
+        /** @type { number} */
+        this.field1;
+        // Sickle: end stub declarations.
+    }
+}
diff --git a/test_files/fields_no_ctor.ts b/test_files/fields_no_ctor.ts
new file mode 100644
index 000000000..7e837435f
--- /dev/null
+++ b/test_files/fields_no_ctor.ts
@@ -0,0 +1,3 @@
+class NoCtor {
+  field1: number;
+}