diff --git a/vtkm/exec/CellLocatorBoundingIntervalHierarchy.h b/vtkm/exec/CellLocatorBoundingIntervalHierarchy.h
index c314f18d8..620c7754d 100644
--- a/vtkm/exec/CellLocatorBoundingIntervalHierarchy.h
+++ b/vtkm/exec/CellLocatorBoundingIntervalHierarchy.h
@@ -107,7 +107,7 @@ public:
     cellId = -1;
 
     //Check the last cell.
-    if (lastCell.CellId != -1)
+    if ((lastCell.CellId >= 0) && (lastCell.CellId < this->CellSet.GetNumberOfElements()))
     {
       if (this->PointInCell(point, lastCell.CellId, parametric) == vtkm::ErrorCode::Success)
       {
@@ -117,7 +117,7 @@ public:
     }
 
     //Check the last leaf node.
-    if (lastCell.NodeIdx != -1)
+    if ((lastCell.NodeIdx >= 0) && (lastCell.NodeIdx < this->Nodes.GetNumberOfValues()))
     {
       const auto& node = this->Nodes.Get(lastCell.NodeIdx);
       VTKM_ASSERT(node.ChildIndex < 0); //should be a leaf node.
diff --git a/vtkm/exec/CellLocatorTwoLevel.h b/vtkm/exec/CellLocatorTwoLevel.h
index cafafaaba..d432c98f7 100644
--- a/vtkm/exec/CellLocatorTwoLevel.h
+++ b/vtkm/exec/CellLocatorTwoLevel.h
@@ -174,7 +174,7 @@ public:
   {
     vtkm::Vec3f pc;
     //See if point is inside the last cell.
-    if (lastCell.CellId != -1 &&
+    if ((lastCell.CellId >= 0) && (lastCell.CellId < this->CellSet.GetNumberOfElements()) &&
         this->PointInCell(point, lastCell.CellId, pc) == vtkm::ErrorCode::Success)
     {
       parametric = pc;
@@ -183,7 +183,7 @@ public:
     }
 
     //See if it's in the last leaf.
-    if (lastCell.LeafIdx != -1 &&
+    if ((lastCell.LeafIdx >= 0) && (lastCell.LeafIdx < this->CellCount.GetNumberOfValues()) &&
         this->PointInLeaf(point, lastCell.LeafIdx, cellId, pc) == vtkm::ErrorCode::Success)
     {
       parametric = pc;