diff --git a/modules/libpr0n/public/imgIContainer.idl b/modules/libpr0n/public/imgIContainer.idl
index bc4305d05a1..4b41cdae804 100644
--- a/modules/libpr0n/public/imgIContainer.idl
+++ b/modules/libpr0n/public/imgIContainer.idl
@@ -81,12 +81,14 @@ native gfxGraphicsFilter(gfxPattern::GraphicsFilter);
 interface imgIContainer : nsISupports
 {
   /**
-   * The width of the container rectangle.
+   * The width of the container rectangle.  In the case of any error,
+   * zero is returned, and an exception will be thrown.
    */
   readonly attribute PRInt32 width;
 
   /**
-   * The height of the container rectangle.
+   * The height of the container rectangle.  In the case of any error,
+   * zero is returned, and an exception will be thrown.
    */
   readonly attribute PRInt32 height;
 
diff --git a/modules/libpr0n/src/RasterImage.cpp b/modules/libpr0n/src/RasterImage.cpp
index 4c6e9423fc1..7b7b3f343e3 100644
--- a/modules/libpr0n/src/RasterImage.cpp
+++ b/modules/libpr0n/src/RasterImage.cpp
@@ -389,8 +389,10 @@ RasterImage::GetWidth(PRInt32 *aWidth)
 {
   NS_ENSURE_ARG_POINTER(aWidth);
 
-  if (mError)
+  if (mError) {
+    *aWidth = 0;
     return NS_ERROR_FAILURE;
+  }
 
   *aWidth = mSize.width;
   return NS_OK;
@@ -403,8 +405,10 @@ RasterImage::GetHeight(PRInt32 *aHeight)
 {
   NS_ENSURE_ARG_POINTER(aHeight);
 
-  if (mError)
+  if (mError) {
+    *aHeight = 0;
     return NS_ERROR_FAILURE;
+  }
 
   *aHeight = mSize.height;
   return NS_OK;