diff --git a/content/base/src/nsGkAtomList.h b/content/base/src/nsGkAtomList.h
index abce1f00dc2..4824a948b59 100644
--- a/content/base/src/nsGkAtomList.h
+++ b/content/base/src/nsGkAtomList.h
@@ -921,6 +921,7 @@ GK_ATOM(statedatasource, "statedatasource")
 GK_ATOM(staticHint, "staticHint")
 GK_ATOM(statusbar, "statusbar")
 GK_ATOM(statustext, "statustext")
+GK_ATOM(step, "step")
 GK_ATOM(stop, "stop")
 GK_ATOM(stretch, "stretch")
 GK_ATOM(strike, "strike")
diff --git a/content/html/content/src/nsHTMLInputElement.cpp b/content/html/content/src/nsHTMLInputElement.cpp
index b0ac0ebadee..f0c4645596a 100644
--- a/content/html/content/src/nsHTMLInputElement.cpp
+++ b/content/html/content/src/nsHTMLInputElement.cpp
@@ -862,6 +862,7 @@ NS_IMPL_STRING_ATTR(nsHTMLInputElement, Name, name)
 NS_IMPL_BOOL_ATTR(nsHTMLInputElement, ReadOnly, readonly)
 NS_IMPL_BOOL_ATTR(nsHTMLInputElement, Required, required)
 NS_IMPL_URI_ATTR(nsHTMLInputElement, Src, src)
+NS_IMPL_STRING_ATTR(nsHTMLInputElement, Step, step)
 NS_IMPL_INT_ATTR(nsHTMLInputElement, TabIndex, tabindex)
 NS_IMPL_STRING_ATTR(nsHTMLInputElement, UseMap, usemap)
 //NS_IMPL_STRING_ATTR(nsHTMLInputElement, Value, value)
diff --git a/content/html/content/test/forms/test_input_attributes_reflection.html b/content/html/content/test/forms/test_input_attributes_reflection.html
index 94b1a32490b..ab77ab872a1 100644
--- a/content/html/content/test/forms/test_input_attributes_reflection.html
+++ b/content/html/content/test/forms/test_input_attributes_reflection.html
@@ -179,7 +179,10 @@ reflectUnsignedInt({
 // TODO: src (URL)
 
 // .step
-todo("step" in document.createElement("input"), "step isn't implemented yet");
+reflectString({
+  element: document.createElement('input'),
+  attribute: 'step',
+});
 
 // .type
 reflectLimitedEnumerated({
diff --git a/dom/interfaces/html/nsIDOMHTMLInputElement.idl b/dom/interfaces/html/nsIDOMHTMLInputElement.idl
index 1c94d43038d..9313260b611 100644
--- a/dom/interfaces/html/nsIDOMHTMLInputElement.idl
+++ b/dom/interfaces/html/nsIDOMHTMLInputElement.idl
@@ -20,7 +20,7 @@ interface nsIDOMValidityState;
   * http://www.whatwg.org/specs/web-apps/current-work/
   */
 
-[scriptable, uuid(261b0fa1-dfcc-445d-8ac8-6b3817ec63cb)]
+[scriptable, uuid(e20b7e26-e952-4bba-9192-99bd1a4b3816)]
 interface nsIDOMHTMLInputElement : nsIDOMHTMLElement
 {
            attribute DOMString             accept;
@@ -55,6 +55,7 @@ interface nsIDOMHTMLInputElement : nsIDOMHTMLElement
            attribute DOMString             placeholder;
            attribute boolean               readOnly;
            attribute boolean               required;
+           attribute DOMString             step;
 
            attribute DOMString             align;