diff --git a/layout/generic/nsImageFrame.cpp b/layout/generic/nsImageFrame.cpp
index 962f1f2a93a0..7a60b620b640 100644
--- a/layout/generic/nsImageFrame.cpp
+++ b/layout/generic/nsImageFrame.cpp
@@ -905,7 +905,12 @@ nsImageFrame::Reflow(nsPresContext* aPresContext,
nsRect altFeedbackSize(0, 0,
nsPresContext::CSSPixelsToAppUnits(ICON_SIZE+2*(ICON_PADDING+ALT_BORDER_WIDTH)),
nsPresContext::CSSPixelsToAppUnits(ICON_SIZE+2*(ICON_PADDING+ALT_BORDER_WIDTH)));
- aMetrics.mOverflowAreas.UnionAllWith(altFeedbackSize);
+ // We include the altFeedbackSize in our visual overflow, but not in our
+ // scrollable overflow, since it doesn't really need to be scrolled to
+ // outside the image.
+ MOZ_STATIC_ASSERT(eOverflowType_LENGTH == 2, "Unknown overflow types?");
+ nsRect& visualOverflow = aMetrics.VisualOverflow();
+ visualOverflow.UnionRect(visualOverflow, altFeedbackSize);
}
FinishAndStoreOverflow(&aMetrics);
diff --git a/layout/generic/test/Makefile.in b/layout/generic/test/Makefile.in
index 63e4b493a069..7f1a70ba81d0 100644
--- a/layout/generic/test/Makefile.in
+++ b/layout/generic/test/Makefile.in
@@ -104,6 +104,7 @@ MOCHITEST_FILES = \
test_bug784410.html \
test_bug785324.html \
test_bug791616.html \
+ test_bug831780.html \
$(NULL)
MOCHITEST_CHROME_FILES = \
diff --git a/layout/generic/test/test_bug831780.html b/layout/generic/test/test_bug831780.html
new file mode 100644
index 000000000000..1173d8e03008
--- /dev/null
+++ b/layout/generic/test/test_bug831780.html
@@ -0,0 +1,32 @@
+
+
+
+
+
+ Test for Bug 831780
+
+
+
+
+Mozilla Bug 831780
+
+
+ ![]()
+
+
+
+
+
+
+
+
+