diff --git a/layout/generic/nsBlockFrame.cpp b/layout/generic/nsBlockFrame.cpp
index 9447391365c1..7fc01e8e302d 100644
--- a/layout/generic/nsBlockFrame.cpp
+++ b/layout/generic/nsBlockFrame.cpp
@@ -2514,7 +2514,7 @@ nsBlockFrame::PullFrame(nsBlockReflowState& aState,
 {
   // First check our remaining lines.
   if (end_lines() != aLine.next()) {
-    return PullFrameFrom(aState, aLine, this, aLine.next());
+    return PullFrameFrom(aLine, this, aLine.next());
   }
 
   NS_ASSERTION(!GetOverflowLines(),
@@ -2527,8 +2527,7 @@ nsBlockFrame::PullFrame(nsBlockReflowState& aState,
       nextInFlow->DrainSelfOverflowList();
     }
     if (!nextInFlow->mLines.empty()) {
-      return PullFrameFrom(aState, aLine, nextInFlow,
-                           nextInFlow->mLines.begin());
+      return PullFrameFrom(aLine, nextInFlow, nextInFlow->mLines.begin());
     }
     nextInFlow = static_cast<nsBlockFrame*>(nextInFlow->GetNextInFlow());
     aState.mNextInFlow = nextInFlow;
@@ -2538,8 +2537,7 @@ nsBlockFrame::PullFrame(nsBlockReflowState& aState,
 }
 
 nsIFrame*
-nsBlockFrame::PullFrameFrom(nsBlockReflowState&  aState,
-                            nsLineBox*           aLine,
+nsBlockFrame::PullFrameFrom(nsLineBox*           aLine,
                             nsBlockFrame*        aFromContainer,
                             nsLineList::iterator aFromLine)
 {
@@ -2562,10 +2560,9 @@ nsBlockFrame::PullFrameFrom(nsBlockReflowState&  aState,
   nsIFrame* newFirstChild = frame->GetNextSibling();
 
   if (aFromContainer != this) {
-    NS_ASSERTION(aState.mPrevChild == aLine->LastChild(),
-      "mPrevChild should be the LastChild of the line we are adding to");
     // The frame is being pulled from a next-in-flow; therefore we
     // need to add it to our sibling list.
+    MOZ_ASSERT(aLine == mLines.back());
     MOZ_ASSERT(aFromLine == aFromContainer->mLines.begin(),
                "should only pull from first line");
     aFromContainer->mFrames.RemoveFrame(frame);
@@ -2573,14 +2570,15 @@ nsBlockFrame::PullFrameFrom(nsBlockReflowState&  aState,
     // When pushing and pulling frames we need to check for whether any
     // views need to be reparented.
     ReparentFrame(frame, aFromContainer, this);
-    mFrames.InsertFrame(nullptr, aState.mPrevChild, frame);
+    mFrames.AppendFrame(nullptr, frame);
 
     // The frame might have (or contain) floats that need to be
     // brought over too.
     ReparentFloats(frame, aFromContainer, true);
+  } else {
+    MOZ_ASSERT(aLine == aFromLine.prev());
   }
-  // when aFromContainer is 'this', then aLine->LastChild()'s next sibling
-  // is already set correctly.
+
   aLine->NoteFrameAdded(frame);
   fromLine->NoteFrameRemoved(frame);
 
diff --git a/layout/generic/nsBlockFrame.h b/layout/generic/nsBlockFrame.h
index ff29f661dbc2..82ec0f9fbd0c 100644
--- a/layout/generic/nsBlockFrame.h
+++ b/layout/generic/nsBlockFrame.h
@@ -693,8 +693,7 @@ protected:
    *
    * @return the pulled frame or nullptr
    */
-  nsIFrame* PullFrameFrom(nsBlockReflowState&  aState,
-                          nsLineBox*           aLine,
+  nsIFrame* PullFrameFrom(nsLineBox*           aLine,
                           nsBlockFrame*        aFromContainer,
                           nsLineList::iterator aFromLine);