diff --git a/layout/generic/nsGridContainerFrame.cpp b/layout/generic/nsGridContainerFrame.cpp
index 0efc9540536e..9482acf59454 100644
--- a/layout/generic/nsGridContainerFrame.cpp
+++ b/layout/generic/nsGridContainerFrame.cpp
@@ -4565,18 +4565,21 @@ Maybe<nsGridContainerFrame::Fragmentainer>
 nsGridContainerFrame::GetNearestFragmentainer(const GridReflowInput& aState) const
 {
   Maybe<nsGridContainerFrame::Fragmentainer> data;
-  WritingMode wm = aState.mWM;
   const ReflowInput* gridRI = aState.mReflowInput;
-  const ReflowInput* cbRS = gridRI->mCBReflowInput;
-  for ( ; cbRS; cbRS = cbRS->mCBReflowInput) {
-    nsIScrollableFrame* sf = do_QueryFrame(cbRS->mFrame);
+  if (gridRI->AvailableBSize() == NS_UNCONSTRAINEDSIZE) {
+    return data;
+  }
+  WritingMode wm = aState.mWM;
+  const ReflowInput* cbRI = gridRI->mCBReflowInput;
+  for ( ; cbRI; cbRI = cbRI->mCBReflowInput) {
+    nsIScrollableFrame* sf = do_QueryFrame(cbRI->mFrame);
     if (sf) {
       break;
     }
-    if (wm.IsOrthogonalTo(cbRS->GetWritingMode())) {
+    if (wm.IsOrthogonalTo(cbRI->GetWritingMode())) {
       break;
     }
-    nsIAtom* frameType = cbRS->mFrame->GetType();
+    nsIAtom* frameType = cbRI->mFrame->GetType();
     if ((frameType == nsGkAtoms::canvasFrame &&
          PresContext()->IsPaginated()) ||
         frameType == nsGkAtoms::columnSetFrame) {
diff --git a/layout/tables/nsTableFrame.cpp b/layout/tables/nsTableFrame.cpp
index ebf53ff1183e..eaedc0d5cbd7 100644
--- a/layout/tables/nsTableFrame.cpp
+++ b/layout/tables/nsTableFrame.cpp
@@ -3222,8 +3222,11 @@ nsTableFrame::ReflowChildren(TableReflowInput& aReflowInput,
       // Remember where we just were in case we end up pushing children
       prevKidFrame = kidFrame;
 
+      MOZ_ASSERT(!NS_FRAME_IS_NOT_COMPLETE(aStatus) || isPaginated,
+                 "Table contents should only fragment in paginated contexts");
+
       // Special handling for incomplete children
-      if (NS_FRAME_IS_NOT_COMPLETE(aStatus)) {
+      if (isPaginated && NS_FRAME_IS_NOT_COMPLETE(aStatus)) {
         nsIFrame* kidNextInFlow = kidFrame->GetNextInFlow();
         if (!kidNextInFlow) {
           // The child doesn't have a next-in-flow so create a continuing