diff --git a/content/xbl/src/nsBindingManager.cpp b/content/xbl/src/nsBindingManager.cpp
index c383f61f7d8..e4d1bf2e569 100644
--- a/content/xbl/src/nsBindingManager.cpp
+++ b/content/xbl/src/nsBindingManager.cpp
@@ -77,6 +77,7 @@
 #include "nsDOMCID.h"
 #include "nsIDOMScriptObjectFactory.h"
 #include "nsIScriptGlobalObject.h"
+#include "nsTHashtable.h"
 
 #include "nsIScriptContext.h"
 #include "nsBindingManager.h"
@@ -1234,8 +1235,7 @@ nsBindingManager::GetBindingImplementation(nsIContent* aContent, REFNSIID aIID,
 }
 
 nsresult
-nsBindingManager::WalkRules(nsStyleSet* aStyleSet,
-                            nsIStyleRuleProcessor::EnumFunc aFunc,
+nsBindingManager::WalkRules(nsIStyleRuleProcessor::EnumFunc aFunc,
                             RuleProcessorData* aData,
                             PRBool* aCutOffInheritance)
 {
@@ -1280,6 +1280,63 @@ nsBindingManager::WalkRules(nsStyleSet* aStyleSet,
   return NS_OK;
 }
 
+typedef nsTHashtable<nsVoidPtrHashKey> RuleProcessorSet;
+
+PR_STATIC_CALLBACK(PLDHashOperator)
+EnumRuleProcessors(nsISupports *aKey, nsXBLBinding *aBinding, void* aClosure)
+{
+  RuleProcessorSet *set = static_cast<RuleProcessorSet*>(aClosure);
+  for (nsXBLBinding *binding = aBinding; binding;
+       binding = binding->GetBaseBinding()) {
+    nsIStyleRuleProcessor *ruleProc =
+      binding->PrototypeBinding()->GetRuleProcessor();
+    if (ruleProc) {
+      if (!set->IsInitialized() && !set->Init(16))
+        return PL_DHASH_STOP;
+      set->PutEntry(ruleProc);
+    }
+  }
+  return PL_DHASH_NEXT;
+}
+
+struct MediumFeaturesChangedData {
+  nsPresContext *mPresContext;
+  PRBool *mRulesChanged;
+};
+
+PR_STATIC_CALLBACK(PLDHashOperator)
+EnumMediumFeaturesChanged(nsVoidPtrHashKey *aKey, void* aClosure)
+{
+  nsIStyleRuleProcessor *ruleProcessor =
+    static_cast<nsIStyleRuleProcessor*>(const_cast<void*>(aKey->GetKey()));
+  MediumFeaturesChangedData *data =
+    static_cast<MediumFeaturesChangedData*>(aClosure);
+
+  PRBool thisChanged = PR_FALSE;
+  ruleProcessor->MediumFeaturesChanged(data->mPresContext, &thisChanged);
+  *data->mRulesChanged = *data->mRulesChanged || thisChanged;
+
+  return PL_DHASH_NEXT;
+}
+
+nsresult
+nsBindingManager::MediumFeaturesChanged(nsPresContext* aPresContext,
+                                        PRBool* aRulesChanged)
+{
+  *aRulesChanged = PR_FALSE;
+  if (!mBindingTable.IsInitialized())
+    return NS_OK;
+
+  RuleProcessorSet set;
+  mBindingTable.EnumerateRead(EnumRuleProcessors, &set);
+  if (!set.IsInitialized())
+    return NS_OK;
+
+  MediumFeaturesChangedData data = { aPresContext, aRulesChanged };
+  set.EnumerateEntries(EnumMediumFeaturesChanged, &data);
+  return NS_OK;
+}
+
 PRBool
 nsBindingManager::ShouldBuildChildFrames(nsIContent* aContent)
 {
diff --git a/content/xbl/src/nsBindingManager.h b/content/xbl/src/nsBindingManager.h
index 8651f0e42f3..6009b7e8961 100755
--- a/content/xbl/src/nsBindingManager.h
+++ b/content/xbl/src/nsBindingManager.h
@@ -184,10 +184,16 @@ public:
   PRBool ShouldBuildChildFrames(nsIContent* aContent);
 
   // Style rule methods
-  nsresult WalkRules(nsStyleSet* aStyleSet, 
-                     nsIStyleRuleProcessor::EnumFunc aFunc,
+  nsresult WalkRules(nsIStyleRuleProcessor::EnumFunc aFunc,
                      RuleProcessorData* aData,
                      PRBool* aCutOffInheritance);
+  /**
+   * Do any processing that needs to happen as a result of a change in
+   * the characteristics of the medium, and return whether this rule
+   * processor's rules have changed (e.g., because of media queries).
+   */
+  nsresult MediumFeaturesChanged(nsPresContext* aPresContext,
+                                 PRBool* aRulesChanged);
 
   NS_HIDDEN_(void) Traverse(nsIContent *aContent,
                             nsCycleCollectionTraversalCallback &cb);
diff --git a/layout/style/nsStyleSet.cpp b/layout/style/nsStyleSet.cpp
index adb2ef6de2b..84708fc89b7 100644
--- a/layout/style/nsStyleSet.cpp
+++ b/layout/style/nsStyleSet.cpp
@@ -533,8 +533,7 @@ nsStyleSet::FileRules(nsIStyleRuleProcessor::EnumFunc aCollectorFunc,
   PRBool cutOffInheritance = PR_FALSE;
   if (mBindingManager) {
     // We can supply additional document-level sheets that should be walked.
-    mBindingManager->WalkRules(this, aCollectorFunc, aData,
-                               &cutOffInheritance);
+    mBindingManager->WalkRules(aCollectorFunc, aData, &cutOffInheritance);
   }
   if (!skipUserStyles && !cutOffInheritance &&
       mRuleProcessors[eDocSheet]) // NOTE: different
@@ -594,7 +593,7 @@ nsStyleSet::WalkRuleProcessors(nsIStyleRuleProcessor::EnumFunc aFunc,
   PRBool cutOffInheritance = PR_FALSE;
   if (mBindingManager) {
     // We can supply additional document-level sheets that should be walked.
-    mBindingManager->WalkRules(this, aFunc, aData, &cutOffInheritance);
+    mBindingManager->WalkRules(aFunc, aData, &cutOffInheritance);
   }
   if (!skipUserStyles && !cutOffInheritance &&
       mRuleProcessors[eDocSheet]) // NOTE: different
@@ -968,7 +967,6 @@ PRBool
 nsStyleSet::MediumFeaturesChanged(nsPresContext* aPresContext)
 {
   // We can't use WalkRuleProcessors without a content node.
-  // XXX We don't notify mBindingManager.  Should we?
   PRBool stylesChanged = PR_FALSE;
   for (PRUint32 i = 0; i < NS_ARRAY_LENGTH(mRuleProcessors); ++i) {
     nsIStyleRuleProcessor *processor = mRuleProcessors[i];
@@ -980,5 +978,11 @@ nsStyleSet::MediumFeaturesChanged(nsPresContext* aPresContext)
     stylesChanged = stylesChanged || thisChanged;
   }
 
+  if (mBindingManager) {
+    PRBool thisChanged = PR_FALSE;
+    mBindingManager->MediumFeaturesChanged(aPresContext, &thisChanged);
+    stylesChanged = stylesChanged || thisChanged;
+  }
+
   return stylesChanged;
 }
diff --git a/layout/style/test/Makefile.in b/layout/style/test/Makefile.in
index e073fb864e6..2f905e0256f 100644
--- a/layout/style/test/Makefile.in
+++ b/layout/style/test/Makefile.in
@@ -104,6 +104,7 @@ _TEST_FILES =	test_acid3_test46.html \
 		test_initial_computation.html \
 		test_initial_storage.html \
 		test_media_queries.html \
+		test_media_queries_dynamic_xbl.html \
 		test_of_type_selectors.xhtml \
 		test_parse_rule.html \
 		test_property_database.html \
@@ -131,6 +132,9 @@ _TEST_FILES =	test_acid3_test46.html \
 		xbl_bindings.xml \
 		empty.html \
 		media_queries_iframe.html \
+		media_queries_dynamic_xbl_binding.xml \
+		media_queries_dynamic_xbl_iframe.html \
+		media_queries_dynamic_xbl_style.css \
 		$(NULL)
 
 
diff --git a/layout/style/test/media_queries_dynamic_xbl_binding.xml b/layout/style/test/media_queries_dynamic_xbl_binding.xml
new file mode 100644
index 00000000000..4b851553909
--- /dev/null
+++ b/layout/style/test/media_queries_dynamic_xbl_binding.xml
@@ -0,0 +1,13 @@
+<?xml version="1.0"?>
+<bindings xmlns="http://www.mozilla.org/xbl">
+  <binding id="binding">
+    <resources>
+      <stylesheet src="media_queries_dynamic_xbl_style.css" />
+    </resources>
+    <content>
+      <html:div xmlns:html="http://www.w3.org/1999/xhtml">
+        <children/>
+      </html:div>
+    </content>
+  </binding>
+</bindings>
diff --git a/layout/style/test/media_queries_dynamic_xbl_iframe.html b/layout/style/test/media_queries_dynamic_xbl_iframe.html
new file mode 100644
index 00000000000..50e8008fa2b
--- /dev/null
+++ b/layout/style/test/media_queries_dynamic_xbl_iframe.html
@@ -0,0 +1,5 @@
+<!DOCTYPE HTML>
+<style type="text/css">
+body { -moz-binding: url(media_queries_dynamic_xbl_binding.xml#binding); }
+</style>
+<p id="para">Hello</p>
diff --git a/layout/style/test/media_queries_dynamic_xbl_style.css b/layout/style/test/media_queries_dynamic_xbl_style.css
new file mode 100644
index 00000000000..5c99c07ee6f
--- /dev/null
+++ b/layout/style/test/media_queries_dynamic_xbl_style.css
@@ -0,0 +1,6 @@
+@media (orientation: portrait) {
+  div { color: purple; }
+}
+@media (orientation: landscape) {
+  div { color: blue; }
+}
diff --git a/layout/style/test/test_media_queries_dynamic_xbl.html b/layout/style/test/test_media_queries_dynamic_xbl.html
new file mode 100644
index 00000000000..7ab8a6d6670
--- /dev/null
+++ b/layout/style/test/test_media_queries_dynamic_xbl.html
@@ -0,0 +1,41 @@
+<!DOCTYPE HTML>
+<html>
+<!--
+https://bugzilla.mozilla.org/show_bug.cgi?id=156716
+-->
+<head>
+  <title>Test for Bug 156716</title>
+  <script type="text/javascript" src="/MochiKit/MochiKit.js"></script>
+  <script type="text/javascript" src="/tests/SimpleTest/SimpleTest.js"></script>
+  <link rel="stylesheet" type="text/css" href="/tests/SimpleTest/test.css" />
+</head>
+<body onload="run()">
+<a target="_blank" href="https://bugzilla.mozilla.org/show_bug.cgi?id=156716">Mozilla Bug 156716</a>
+<iframe id="display" src="media_queries_dynamic_xbl_iframe.html"></iframe>
+<pre id="test">
+<script class="testbody" type="text/javascript">
+
+/** Test for Bug 156716 **/
+
+function run() {
+  var iframe = document.getElementById("display");
+
+  var subdoc = iframe.contentDocument;
+  var subwin = iframe.contentWindow;
+  var p = subdoc.getElementById("para");
+
+  iframe.setAttribute("style", "height: 300px; width: 100px");
+  is(subwin.getComputedStyle(p, "").color, "rgb(128, 0, 128)",
+     "should be purple when portait");
+  iframe.setAttribute("style", "height: 100px; width: 300px");
+  is(subwin.getComputedStyle(p, "").color, "rgb(0, 0, 255)",
+     "should be blue when landscape");
+  SimpleTest.finish();
+}
+SimpleTest.waitForExplicitFinish();
+
+</script>
+</pre>
+</body>
+</html>
+