--- a/layout/generic/nsFlexContainerFrame.cpp
+++ b/layout/generic/nsFlexContainerFrame.cpp
@@ -1076,36 +1076,38 @@ GetFirstNonAnonBoxDescendant(nsIFrame* a
 bool
 IsOrderLEQWithDOMFallback(nsIFrame* aFrame1,
                           nsIFrame* aFrame2)
 {
   MOZ_ASSERT(aFrame1->IsFlexItem() && aFrame2->IsFlexItem(),
              "this method only intended for comparing flex items");
   MOZ_ASSERT(aFrame1->GetParent() == aFrame2->GetParent(),
              "this method only intended for comparing siblings");
-  bool isInLegacyBox = nsFlexContainerFrame::IsLegacyBox(aFrame1->GetParent());
-
   if (aFrame1 == aFrame2) {
     // Anything is trivially LEQ itself, so we return "true" here... but it's
     // probably bad if we end up actually needing this, so let's assert.
     NS_ERROR("Why are we checking if a frame is LEQ itself?");
     return true;
   }
 
-  // If we've got a placeholder frame, use its out-of-flow frame's 'order' val.
-  {
-    nsIFrame* aRealFrame1 = nsPlaceholderFrame::GetRealFrameFor(aFrame1);
-    nsIFrame* aRealFrame2 = nsPlaceholderFrame::GetRealFrameFor(aFrame2);
-
-    int32_t order1 = GetOrderOrBoxOrdinalGroup(aRealFrame1, isInLegacyBox);
-    int32_t order2 = GetOrderOrBoxOrdinalGroup(aRealFrame2, isInLegacyBox);
-
-    if (order1 != order2) {
-      return order1 < order2;
-    }
+  if (aFrame1->GetType() == nsGkAtoms::placeholderFrame ||
+      aFrame2->GetType() == nsGkAtoms::placeholderFrame) {
+    // Treat placeholders (for abspos/fixedpos frames) as LEQ everything.  This
+    // ensures we don't reorder them w.r.t. one another, which is sufficient to
+    // prevent them from noticeably participating in "order" reordering.
+    return true;
+  }
+
+  bool isInLegacyBox = nsFlexContainerFrame::IsLegacyBox(aFrame1->GetParent());
+
+  int32_t order1 = GetOrderOrBoxOrdinalGroup(aFrame1, isInLegacyBox);
+  int32_t order2 = GetOrderOrBoxOrdinalGroup(aFrame2, isInLegacyBox);
+
+  if (order1 != order2) {
+    return order1 < order2;
   }
 
   // The "order" values are equal, so we need to fall back on DOM comparison.
   // For that, we need to dig through any anonymous box wrapper frames to find
   // the actual frame that corresponds to our child content.
   aFrame1 = GetFirstNonAnonBoxDescendant(aFrame1);
   aFrame2 = GetFirstNonAnonBoxDescendant(aFrame2);
   MOZ_ASSERT(aFrame1 && aFrame2,
@@ -1160,24 +1162,29 @@ IsOrderLEQWithDOMFallback(nsIFrame* aFra
 bool
 IsOrderLEQ(nsIFrame* aFrame1,
            nsIFrame* aFrame2)
 {
   MOZ_ASSERT(aFrame1->IsFlexItem() && aFrame2->IsFlexItem(),
              "this method only intended for comparing flex items");
   MOZ_ASSERT(aFrame1->GetParent() == aFrame2->GetParent(),
              "this method only intended for comparing siblings");
+
+  if (aFrame1->GetType() == nsGkAtoms::placeholderFrame ||
+      aFrame2->GetType() == nsGkAtoms::placeholderFrame) {
+    // Treat placeholders (for abspos/fixedpos frames) as LEQ everything.  This
+    // ensures we don't reorder them w.r.t. one another, which is sufficient to
+    // prevent them from noticeably participating in "order" reordering.
+    return true;
+  }
+
   bool isInLegacyBox = nsFlexContainerFrame::IsLegacyBox(aFrame1->GetParent());
 
-  // If we've got a placeholder frame, use its out-of-flow frame's 'order' val.
-  nsIFrame* aRealFrame1 = nsPlaceholderFrame::GetRealFrameFor(aFrame1);
-  nsIFrame* aRealFrame2 = nsPlaceholderFrame::GetRealFrameFor(aFrame2);
-
-  int32_t order1 = GetOrderOrBoxOrdinalGroup(aRealFrame1, isInLegacyBox);
-  int32_t order2 = GetOrderOrBoxOrdinalGroup(aRealFrame2, isInLegacyBox);
+  int32_t order1 = GetOrderOrBoxOrdinalGroup(aFrame1, isInLegacyBox);
+  int32_t order2 = GetOrderOrBoxOrdinalGroup(aFrame2, isInLegacyBox);
 
   return order1 <= order2;
 }
 
 bool
 nsFlexContainerFrame::IsHorizontal()
 {
   const FlexboxAxisTracker axisTracker(this, GetWritingMode());