diff --git a/types/lib/legacy/polymer.dom.d.ts b/types/lib/legacy/polymer.dom.d.ts
index e0992bfe64..fcb45e7f2e 100644
--- a/types/lib/legacy/polymer.dom.d.ts
+++ b/types/lib/legacy/polymer.dom.d.ts
@@ -47,6 +47,11 @@ declare namespace Polymer {
      */
     readonly activeElement: Node|null|undefined;
 
+    /**
+     * @param node Node for which to create a Polymer.dom helper object.
+     */
+    constructor(node: Node|null);
+
     /**
      * Returns an instance of `Polymer.FlattenedNodesObserver` that
      * listens for node changes on this element.
@@ -176,4 +181,5 @@ declare class EventApi {
    * Returns the `composedPath` for this event.
    */
   readonly path: EventTarget[];
+  constructor(event: any);
 }
diff --git a/types/lib/utils/debounce.d.ts b/types/lib/utils/debounce.d.ts
index d8ee1eabc2..80728e08bb 100644
--- a/types/lib/utils/debounce.d.ts
+++ b/types/lib/utils/debounce.d.ts
@@ -15,6 +15,7 @@
 declare namespace Polymer {
 
   class Debouncer {
+    constructor();
 
     /**
      * Creates a debouncer if no debouncer is passed as a parameter
diff --git a/types/lib/utils/flattened-nodes-observer.d.ts b/types/lib/utils/flattened-nodes-observer.d.ts
index 32915b4bd3..e02f483b92 100644
--- a/types/lib/utils/flattened-nodes-observer.d.ts
+++ b/types/lib/utils/flattened-nodes-observer.d.ts
@@ -54,6 +54,13 @@ declare namespace Polymer {
    */
   class FlattenedNodesObserver {
 
+    /**
+     * @param target Node on which to listen for changes.
+     * @param callback Function called when there are additions
+     * or removals from the target's list of flattened nodes.
+     */
+    constructor(target: _Element|null, callback: ((p0: _Element, p1: {target: _Element, addedNodes: _Element[], removedNodes: _Element[]}) => void)|null);
+
     /**
      * Returns the list of flattened nodes for the given `node`.
      * This list consists of a node's children and, for any children
diff --git a/types/lib/utils/html-tag.d.ts b/types/lib/utils/html-tag.d.ts
index 5c138ccc6e..7c20bf1bc8 100644
--- a/types/lib/utils/html-tag.d.ts
+++ b/types/lib/utils/html-tag.d.ts
@@ -17,6 +17,7 @@
  */
 declare class LiteralString {
   value: string;
+  constructor(string: any);
 
   /**
    * @returns LiteralString string value