diff --git a/data/scenarios/Testing/1780-structure-merge-expansion/00-ORDER.txt b/data/scenarios/Testing/1780-structure-merge-expansion/00-ORDER.txt
index b551229c8..37cfa0703 100644
--- a/data/scenarios/Testing/1780-structure-merge-expansion/00-ORDER.txt
+++ b/data/scenarios/Testing/1780-structure-merge-expansion/00-ORDER.txt
@@ -3,3 +3,4 @@ root-map-expansion.yaml
 structure-composition.yaml
 sequential-placement.yaml
 coordinate-offset-propagation.yaml
+simultaneous-north-and-west-offset.yaml
diff --git a/data/scenarios/Testing/1780-structure-merge-expansion/simultaneous-north-and-west-offset.yaml b/data/scenarios/Testing/1780-structure-merge-expansion/simultaneous-north-and-west-offset.yaml
new file mode 100644
index 000000000..3619d7aba
--- /dev/null
+++ b/data/scenarios/Testing/1780-structure-merge-expansion/simultaneous-north-and-west-offset.yaml
@@ -0,0 +1,59 @@
+version: 1
+name: Northwest sibling structure coordinate offsets
+author: Karl Ostmo
+description: |
+  Make sure that the second sibling isn't garbled when there
+  is a simultaneous negative-x and postive-y offset on the first sibling.
+robots:
+  - name: base
+    dir: north
+creative: true
+objectives:
+  - goal:
+      - Must have 3 of each color visible
+    condition: |
+      return false
+solution: |
+  noop
+known: [boulder, log, pixel (R), pixel (G), pixel (B), gold]
+world:
+  structures:
+    - name: micro
+      structure:
+        mask: '.'
+        palette:
+          'x': [stone, gold]
+        map: |
+          x
+    - name: block
+      structure:
+        mask: '.'
+        palette:
+          'x': [stone, pixel (R)]
+        map: |
+          xx
+          xx
+    - name: master
+      structure:
+        mask: '.'
+        placements:
+          - src: micro
+            offset: [-1, 1]
+          - src: block
+        map: ""
+  dsl: |
+    overlay
+    [ {grass}
+    , mask (y > -4 && y < 4 || x > -4 && x < 4) {stone}
+    , mask (y > -2 && y < 2 || x > -2 && x < 2) {ice}
+    , mask (y > -1 && y < 1 || x > -1 && x < 1) {dirt}
+    ]
+  palette:
+    'Ω': [grass, erase, base]
+  mask: '.'
+  placements:
+    - src: master
+      offset: [0, 0]
+  upperleft: [0, 0]
+  map: |
+    Ω
diff --git a/test/unit/TestOverlay.hs b/test/unit/TestOverlay.hs
index 7d728ab6e..1481c3f79 100644
--- a/test/unit/TestOverlay.hs
+++ b/test/unit/TestOverlay.hs
@@ -6,6 +6,7 @@
 -- Unit tests for generic grid overlay logic
 module TestOverlay where
 
+import Control.Monad (when)
 import Data.Text (Text)
 import Swarm.Game.Location
 import Swarm.Game.Scenario.Topography.Grid
@@ -17,8 +18,16 @@ import Swarm.Game.Scenario.Topography.Structure.Overlay
 import Test.Tasty
 import Test.Tasty.HUnit
 
+debugRenderGrid :: Bool
+debugRenderGrid = True
+
 -- * Example grids
 
+-- | Single cell
+oneByOneGrid :: [[Int]]
+oneByOneGrid = [[0]]
+
+
 -- | Single row with two columns
 oneByTwoGrid :: [[Int]]
 oneByTwoGrid = [[5, 6]]
@@ -87,6 +96,15 @@ testOverlay =
                 ]
                 (Location 2 0)
             ]
+        , testGroup
+            "Northwesterly offset of first sibling"
+            [ mkOverlaySequenceOriginTest
+                "positive first south of second"
+                [ placeUnshifted "sibling1" (Location (-1) 1) oneByOneGrid
+                , placeUnshifted "sibling2" (Location 0 0) twoByTwoGrid
+                ]
+                (Location 1 (-1))
+            ]
         ]
     ]
 
@@ -122,11 +140,17 @@ mkOverlaySequenceTest ::
   TestTree
 mkOverlaySequenceTest f testLabel overlays expectedBaseLoc =
   testCase testLabel $ do
+
+    when debugRenderGrid $
+      renderGridResult eitherResultGrid
+
     assertEqual "Base loc wrong" (Right expectedBaseLoc) $
-      f . getGridFromMergedStructure <$> eitherResult
+      f <$> eitherResultGrid
  where
   baseArea = PositionedGrid (Location 0 0) (EmptyGrid :: Grid (Maybe Int))
 
+  eitherResultGrid = getGridFromMergedStructure <$> eitherResult
+
   eitherResult =
     foldLayer
       mempty
@@ -134,8 +158,9 @@ mkOverlaySequenceTest f testLabel overlays expectedBaseLoc =
       overlays
       []
 
-  getGridFromMergedStructure :: MergedStructure c -> PositionedGrid c
-  getGridFromMergedStructure (MergedStructure g _ _) = g
+
+getGridFromMergedStructure :: MergedStructure c -> PositionedGrid c
+getGridFromMergedStructure (MergedStructure g _ _) = g
 
 -- | Place an structure at an offset.
 -- The structure's local origin is (0, 0).
@@ -165,3 +190,10 @@ place localOrigin theName placementOffset g =
       mempty
       mempty
       mempty
+
+renderGridResult :: Either a (PositionedGrid (Maybe Int)) -> IO ()
+renderGridResult eitherResult = case eitherResult of
+  Right pg -> do
+      print pg
+      print $ getRows $ gridContent pg
+  Left _ -> return ()
\ No newline at end of file