diff --git a/accessible/src/base/nsAccessible.cpp b/accessible/src/base/nsAccessible.cpp
index a4f1bcd87b4..b124efc466c 100644
--- a/accessible/src/base/nsAccessible.cpp
+++ b/accessible/src/base/nsAccessible.cpp
@@ -3223,7 +3223,7 @@ nsAccessible::GetAttrValue(nsIAtom *aProperty, double *aValue)
   NS_ENSURE_ARG_POINTER(aValue);
   *aValue = 0;
 
-  if (!mDOMNode)
+  if (IsDefunct())
     return NS_ERROR_FAILURE;  // Node already shut down
 
  if (!mRoleMapEntry || mRoleMapEntry->valueRule == eNoValue)
@@ -3232,12 +3232,19 @@ nsAccessible::GetAttrValue(nsIAtom *aProperty, double *aValue)
   nsCOMPtr<nsIContent> content(do_QueryInterface(mDOMNode));
   NS_ENSURE_STATE(content);
 
-  PRInt32 result = NS_OK;
-  nsAutoString value;
-  if (content->GetAttr(kNameSpaceID_None, aProperty, value))
-    *aValue = value.ToFloat(&result);
+  nsAutoString attrValue;
+  content->GetAttr(kNameSpaceID_None, aProperty, attrValue);
 
-  return result;
+  // Return zero value if there is no attribute or its value is empty.
+  if (attrValue.IsEmpty())
+    return NS_OK;
+
+  PRInt32 error = NS_OK;
+  double value = attrValue.ToFloat(&error);
+  if (NS_SUCCEEDED(error))
+    *aValue = value;
+
+  return NS_OK;
 }
 
 PRUint32
diff --git a/accessible/src/xul/nsXULFormControlAccessible.cpp b/accessible/src/xul/nsXULFormControlAccessible.cpp
index 8564ab76a20..e15a8d3d535 100644
--- a/accessible/src/xul/nsXULFormControlAccessible.cpp
+++ b/accessible/src/xul/nsXULFormControlAccessible.cpp
@@ -579,16 +579,25 @@ nsXULProgressMeterAccessible::GetCurrentValue(double *aCurrentValue)
 
   nsCOMPtr<nsIContent> content(do_QueryInterface(mDOMNode));
 
-  nsAutoString currentValue;
-  content->GetAttr(kNameSpaceID_None, nsAccessibilityAtoms::value, currentValue);
+  nsAutoString attrValue;
+  content->GetAttr(kNameSpaceID_None, nsAccessibilityAtoms::value, attrValue);
 
-  PRInt32 result = NS_OK;
-  if (content->HasAttr(kNameSpaceID_None, nsAccessibilityAtoms::max))
-    *aCurrentValue = currentValue.ToFloat(&result);
-  else
-    *aCurrentValue = currentValue.ToFloat(&result) / 100;
+  // Return zero value if there is no attribute or its value is empty.
+  if (attrValue.IsEmpty())
+    return NS_OK;
 
-  return result;
+  PRInt32 error = NS_OK;
+  double value = attrValue.ToFloat(&error);
+  if (NS_FAILED(error))
+    return NS_OK; // Zero value because of wrong markup.
+
+  // If no max value then value is between 0 and 1 (refer to GetMaximumValue()
+  // method where max value is assumed to be equal to 1 in this case).
+  if (!content->HasAttr(kNameSpaceID_None, nsAccessibilityAtoms::max))
+    value /= 100;
+
+  *aCurrentValue = value;
+  return NS_OK;
 }
 
 NS_IMETHODIMP
diff --git a/accessible/src/xul/nsXULSliderAccessible.cpp b/accessible/src/xul/nsXULSliderAccessible.cpp
index 75c0ea277e3..5e037aa7a64 100644
--- a/accessible/src/xul/nsXULSliderAccessible.cpp
+++ b/accessible/src/xul/nsXULSliderAccessible.cpp
@@ -49,6 +49,12 @@ nsXULSliderAccessible::nsXULSliderAccessible(nsIDOMNode* aNode,
 {
 }
 
+// nsISupports
+
+NS_IMPL_ISUPPORTS_INHERITED1(nsXULSliderAccessible,
+                             nsAccessibleWrap,
+                             nsIAccessibleValue)
+
 // nsIAccessible
 
 nsresult
@@ -175,7 +181,7 @@ nsXULSliderAccessible::GetSliderAttr(nsIAtom *aName, nsAString& aValue)
 {
   aValue.Truncate();
 
-  if (!mDOMNode)
+  if (IsDefunct())
     return NS_ERROR_FAILURE;
 
   nsCOMPtr<nsIContent> sliderNode(GetSliderNode());
@@ -188,7 +194,7 @@ nsXULSliderAccessible::GetSliderAttr(nsIAtom *aName, nsAString& aValue)
 nsresult
 nsXULSliderAccessible::SetSliderAttr(nsIAtom *aName, const nsAString& aValue)
 {
-  if (!mDOMNode)
+  if (IsDefunct())
     return NS_ERROR_FAILURE;
 
   nsCOMPtr<nsIContent> sliderNode(GetSliderNode());
@@ -204,13 +210,20 @@ nsXULSliderAccessible::GetSliderAttr(nsIAtom *aName, double *aValue)
   NS_ENSURE_ARG_POINTER(aValue);
   *aValue = 0;
 
-  nsAutoString value;
-  nsresult rv = GetSliderAttr(aName, value);
+  nsAutoString attrValue;
+  nsresult rv = GetSliderAttr(aName, attrValue);
   NS_ENSURE_SUCCESS(rv, rv);
 
+  // Return zero value if there is no attribute or its value is empty.
+  if (attrValue.IsEmpty())
+    return NS_OK;
+
   PRInt32 error = NS_OK;
-  *aValue = value.ToFloat(&error);
-  return error;
+  double value = attrValue.ToFloat(&error);
+  if (NS_SUCCEEDED(error))
+    *aValue = value;
+
+  return NS_OK;
 }
 
 nsresult
diff --git a/accessible/src/xul/nsXULSliderAccessible.h b/accessible/src/xul/nsXULSliderAccessible.h
index e46aa1c74d4..514b49266ae 100644
--- a/accessible/src/xul/nsXULSliderAccessible.h
+++ b/accessible/src/xul/nsXULSliderAccessible.h
@@ -48,15 +48,14 @@ class nsXULSliderAccessible : public nsAccessibleWrap
 public:
   nsXULSliderAccessible(nsIDOMNode* aNode, nsIWeakReference* aShell);
 
+  // nsISupports
+  NS_DECL_ISUPPORTS_INHERITED
+
   // nsIAccessible
   NS_IMETHOD GetValue(nsAString& aValue);
 
   // nsIAccessibleValue
-  NS_IMETHOD GetMaximumValue(double *aMaximumValue);
-  NS_IMETHOD GetMinimumValue(double *aMinimumValue);
-  NS_IMETHOD GetMinimumIncrement(double *aMinIncrement);
-  NS_IMETHOD GetCurrentValue(double *aValue);
-  NS_IMETHOD SetCurrentValue(double aValue);
+  NS_DECL_NSIACCESSIBLEVALUE
 
   // nsPIAccessible
   NS_IMETHOD GetAllowsAnonChildAccessibles(PRBool *aAllowsAnonChildren);
diff --git a/accessible/tests/mochitest/Makefile.in b/accessible/tests/mochitest/Makefile.in
index 505a24e682c..9e09e893910 100644
--- a/accessible/tests/mochitest/Makefile.in
+++ b/accessible/tests/mochitest/Makefile.in
@@ -64,6 +64,7 @@ _TEST_FILES =\
 		nsIAccessibleEditableText.js \
 		relations.js \
 		role.js \
+		value.js \
 		test_accessnode_invalidation.html \
 		test_actions_aria.html \
 	$(warning test_actions_inputs.html temporarily disabled) \
@@ -78,7 +79,6 @@ _TEST_FILES =\
 		test_descr.html \
 		test_elm_filectrl.html \
 		test_elm_media.html \
-		test_elm_prgrsmtr.xul \
 		test_elm_txtcntnr.html \
 		test_events_caretmove.html \
 		test_events_mutation.html \
@@ -121,6 +121,7 @@ _TEST_FILES =\
 		test_textattrs.html \
 		test_textboxes.html \
 		test_textboxes.xul \
+		test_value.xul \
 		testTextboxes.js \
 		treeview.js \
 		z_states_frame.html \
diff --git a/accessible/tests/mochitest/common.js b/accessible/tests/mochitest/common.js
index e1066f5ba16..58f7e94fae8 100644
--- a/accessible/tests/mochitest/common.js
+++ b/accessible/tests/mochitest/common.js
@@ -215,7 +215,7 @@ function getAccessible(aAccOrElmOrID, aInterfaces, aElmObj, aDoNotFailIf)
         acc.QueryInterface(aInterfaces[index]);
       } catch (e) {
         if (!(aDoNotFailIf & DONOTFAIL_IF_NO_INTERFACE))
-          ok(false, "Can't query " + aInterfaces[index] + " for " + aID);
+          ok(false, "Can't query " + aInterfaces[index] + " for " + aAccOrElmOrID);
 
         return null;
       }
@@ -226,7 +226,7 @@ function getAccessible(aAccOrElmOrID, aInterfaces, aElmObj, aDoNotFailIf)
   try {
     acc.QueryInterface(aInterfaces);
   } catch (e) {
-    ok(false, "Can't query " + aInterfaces + " for " + aID);
+    ok(false, "Can't query " + aInterfaces + " for " + aAccOrElmOrID);
     return null;
   }
   
diff --git a/accessible/tests/mochitest/test_elm_prgrsmtr.xul b/accessible/tests/mochitest/test_value.xul
similarity index 65%
rename from accessible/tests/mochitest/test_elm_prgrsmtr.xul
rename to accessible/tests/mochitest/test_value.xul
index d5526318d71..fb1c1ffe1ed 100644
--- a/accessible/tests/mochitest/test_elm_prgrsmtr.xul
+++ b/accessible/tests/mochitest/test_value.xul
@@ -13,35 +13,25 @@
 
   <script type="application/javascript"
           src="chrome://mochikit/content/a11y/accessible/common.js" />
+  <script type="application/javascript"
+          src="chrome://mochikit/content/a11y/accessible/value.js" />
 
   <script type="application/javascript">
   <![CDATA[
-    /**
-     * Helper function to test nsIAccessibleValue interface.
-     */
-    function testValue(aAccOrElmOrId, aValue, aCurrValue,
-                       aMinValue, aMaxValue, aMinIncr)
-    {
-      var acc = getAccessible(aAccOrElmOrId, [nsIAccessibleValue]);
-      if (!acc)
-        return;
-
-      is(acc.value, aValue, "Wrong value of " + prettyName(aAccOrElmOrId));
-
-      is(acc.currentValue, aCurrValue,
-         "Wrong current value of " + prettyName(aAccOrElmOrId));
-      is(acc.minimumValue, aMinValue,
-         "Wrong minimum value of " + prettyName(aAccOrElmOrId));
-      is(acc.maximumValue, aMaxValue,
-         "Wrong maximum value of " + prettyName(aAccOrElmOrId));
-      is(acc.minimumIncrement, aMinIncr,
-         "Wrong minimum increment value of " + prettyName(aAccOrElmOrId));
-    }
-
     function doTest()
     {
+      // progressmeter
       testValue("pm1", "50%", .5, 0, 1, 0);
       testValue("pm2", "50%", 500, 0, 1000, 0);
+      testValue("pm3", "0%", 0, 0, 1, 0);
+
+      // scale
+      testValue("sc1", "500", 500, 0, 1000, 10);
+      testValue("sc2", "", 0, 0, 0, 0);
+
+      // aria progressbar
+      testValue("ariapb1", "500", 500, 0, 1000, 0);
+      testValue("ariapb2", "", 0, 0, 0, 0);
 
       SimpleTest.finish();
     }
@@ -65,8 +55,19 @@
       </pre>
     </body>
 
+    <!-- progressmeter -->
     <progressmeter id="pm1" value="50"/>
     <progressmeter id="pm2" value="500" max="1000"/>
+    <progressmeter id="pm3"/>
+
+    <!-- scale -->
+    <scale id="sc1" value="500" max="1000" increment="10"/>
+    <scale id="sc2"/>
+
+    <!-- aria -->
+    <description id="ariapb1" role="progressbar"
+                 aria-valuenow="500" aria-valuemin="0" aria-valuemax="1000"/>
+    <description id="ariapb2" role="progressbar"/>
   </hbox>
 
 </window>
diff --git a/accessible/tests/mochitest/value.js b/accessible/tests/mochitest/value.js
new file mode 100644
index 00000000000..cc9dffe00ac
--- /dev/null
+++ b/accessible/tests/mochitest/value.js
@@ -0,0 +1,32 @@
+////////////////////////////////////////////////////////////////////////////////
+// Public methods
+
+/**
+ * Tests nsIAccessibleValue interface.
+ *
+ * @param aAccOrElmOrId  [in] identifier of accessible
+ * @param aValue         [in] accessible value (nsIAccessible::value)
+ * @param aCurrValue     [in] current value (nsIAccessibleValue::currentValue)
+ * @param aMinValue      [in] minimum value (nsIAccessibleValue::minimumValue)
+ * @param aMaxValue      [in] maximumn value (nsIAccessibleValue::maximumValue)
+ * @param aMinIncr       [in] minimum increment value
+ *                        (nsIAccessibleValue::minimumIncrement)
+ */
+function testValue(aAccOrElmOrId, aValue, aCurrValue,
+                   aMinValue, aMaxValue, aMinIncr)
+{
+  var acc = getAccessible(aAccOrElmOrId, [nsIAccessibleValue]);
+  if (!acc)
+    return;
+
+  is(acc.value, aValue, "Wrong value of " + prettyName(aAccOrElmOrId));
+
+  is(acc.currentValue, aCurrValue,
+     "Wrong current value of " + prettyName(aAccOrElmOrId));
+  is(acc.minimumValue, aMinValue,
+     "Wrong minimum value of " + prettyName(aAccOrElmOrId));
+  is(acc.maximumValue, aMaxValue,
+     "Wrong maximum value of " + prettyName(aAccOrElmOrId));
+  is(acc.minimumIncrement, aMinIncr,
+     "Wrong minimum increment value of " + prettyName(aAccOrElmOrId));
+}