diff --git a/layout/generic/nsGfxScrollFrame.cpp b/layout/generic/nsGfxScrollFrame.cpp
index c3d570e5130c..cec8382a0787 100644
--- a/layout/generic/nsGfxScrollFrame.cpp
+++ b/layout/generic/nsGfxScrollFrame.cpp
@@ -442,19 +442,6 @@ ScrollReflowInput::ScrollReflowInput(nsHTMLScrollFrame* aFrame,
 
     GetScrollbarMetrics(mBoxState, hScrollbarBox, &mHScrollbarMinSize,
                         &mHScrollbarPrefSize);
-
-    // A zero minimum size is a bug with non-overlay scrollbars. That
-    // means we'll always try to place the scrollbar, even if it will ultimately
-    // not fit, see bug 1809630. XUL collapsing is the exception because the
-    // front-end uses it.
-    MOZ_ASSERT(aFrame->PresContext()->UseOverlayScrollbars() ||
-                   hScrollbarBox->IsXULCollapsed() ||
-                   (mHScrollbarMinSize.width && mHScrollbarMinSize.height),
-               "Shouldn't have a zero horizontal min-scrollbar-size");
-    MOZ_ASSERT(mHScrollbarPrefSize.width >= mHScrollbarMinSize.width &&
-                   mHScrollbarPrefSize.height >= mHScrollbarMinSize.height,
-               "Scrollbar pref size should be >= min size");
-
   } else {
     mHScrollbar = ShowScrollbar::Never;
     mHScrollbarAllowedForScrollingVVInsideLV = false;
@@ -465,15 +452,6 @@ ScrollReflowInput::ScrollReflowInput(nsHTMLScrollFrame* aFrame,
 
     GetScrollbarMetrics(mBoxState, vScrollbarBox, &mVScrollbarMinSize,
                         &mVScrollbarPrefSize);
-
-    // See above.
-    MOZ_ASSERT(aFrame->PresContext()->UseOverlayScrollbars() ||
-                   vScrollbarBox->IsXULCollapsed() ||
-                   (mVScrollbarMinSize.width && mVScrollbarMinSize.height),
-               "Shouldn't have a zero vertical min-size");
-    MOZ_ASSERT(mVScrollbarPrefSize.width >= mVScrollbarMinSize.width &&
-                   mVScrollbarPrefSize.height >= mVScrollbarMinSize.height,
-               "Scrollbar pref size should be >= min size");
   } else {
     mVScrollbar = ShowScrollbar::Never;
     mVScrollbarAllowedForScrollingVVInsideLV = false;
diff --git a/widget/ScrollbarDrawingWin.cpp b/widget/ScrollbarDrawingWin.cpp
index c20735a7109e..97b5e9afe474 100644
--- a/widget/ScrollbarDrawingWin.cpp
+++ b/widget/ScrollbarDrawingWin.cpp
@@ -33,6 +33,11 @@ LayoutDeviceIntSize ScrollbarDrawingWin::GetMinimumWidgetSize(
     case StyleAppearance::ScrollbarHorizontal:
     case StyleAppearance::ScrollbarthumbVertical:
     case StyleAppearance::ScrollbarthumbHorizontal: {
+      if ((aAppearance == StyleAppearance::ScrollbarHorizontal ||
+           aAppearance == StyleAppearance::ScrollbarVertical) &&
+          !aPresContext->UseOverlayScrollbars()) {
+        return LayoutDeviceIntSize{};
+      }
       // TODO: for short scrollbars it could be nice if the thumb could shrink
       // under this size.
       auto sizes = GetScrollbarSizes(aPresContext, aFrame);
@@ -41,22 +46,8 @@ LayoutDeviceIntSize ScrollbarDrawingWin::GetMinimumWidgetSize(
           aAppearance == StyleAppearance::ScrollbarthumbHorizontal ||
           aAppearance == StyleAppearance::ScrollbarbuttonLeft ||
           aAppearance == StyleAppearance::ScrollbarbuttonRight;
-      const auto relevantSize =
-          isHorizontal ? sizes.mHorizontal : sizes.mVertical;
-      auto size = LayoutDeviceIntSize{relevantSize, relevantSize};
-      if (aAppearance == StyleAppearance::ScrollbarHorizontal ||
-          aAppearance == StyleAppearance::ScrollbarVertical) {
-        // Always reserve some space in the right direction. Historically we've
-        // reserved 3 times the size in the other axis (one for the thumb, two
-        // for the buttons). We do this even when painting thin scrollbars just
-        // for consistency, though there just one would probably do.
-        if (isHorizontal) {
-          size.width *= 3;
-        } else {
-          size.height *= 3;
-        }
-      }
-      return size;
+      const auto size = isHorizontal ? sizes.mHorizontal : sizes.mVertical;
+      return LayoutDeviceIntSize{size, size};
     }
     default:
       return LayoutDeviceIntSize{};