diff --git a/CHANGES.md b/CHANGES.md
index f6674491e..e01e3f656 100644
--- a/CHANGES.md
+++ b/CHANGES.md
@@ -5,6 +5,7 @@
 ### Issues Fixed/Resolved
 
 * Fixed [#309](https://github.com/CCI-Tools/cate-core/issues/309)
+* Ensure that our tile size matches the expected tile size: resize and fill in background value.
 
 ## Changes in version 0.9.0.dev4
 
diff --git a/cate/util/im/image.py b/cate/util/im/image.py
index 62295c123..a3be991d6 100644
--- a/cate/util/im/image.py
+++ b/cate/util/im/image.py
@@ -654,13 +654,23 @@ def compute_tile(self, tile_x: int, tile_y: int, rectangle: Rectangle2D) -> Tile
         # We do the resampling to lower resolution after loading the data, which is MUCH faster, see note above.
         tile = tile[..., ::zoom, ::zoom]
 
-        actual_tile_size = tile.shape[-1], tile.shape[-2]
-
-        # TODO (forman): ensure that our tile size is w x h: resize and fill in background value.
-        # For time being raise error
-        assert self.tile_size == actual_tile_size, "unexpected tile size: " \
-                                                   "expected %s, but got %s" % (self.tile_size, actual_tile_size)
+        # ensure that our tile size is w x h: resize and fill in background value.
+        return self.pad_tile(tile, self.tile_size)
 
+    @staticmethod
+    def pad_tile(tile: Tile, target_tile_size: Size2D, fill_value: float = np.nan) -> Tile:
+        (target_width, target_height) = target_tile_size
+        tile_width, tile_heigth = tile.shape[-1], tile.shape[-2]
+        if target_width > tile_width:
+            # expand in width
+            h_pad = np.empty((tile_heigth, target_width - tile_width))
+            h_pad.fill(fill_value)
+            tile = np.hstack((tile, h_pad))
+        if target_height > tile_heigth:
+            # expand in height
+            v_pad = np.empty((target_height - tile_heigth, target_width))
+            v_pad.fill(fill_value)
+            tile = np.vstack((tile, v_pad))
         return tile
 
 
diff --git a/test/util/im/test_image.py b/test/util/im/test_image.py
index 54e5b22eb..5f2b0418b 100644
--- a/test/util/im/test_image.py
+++ b/test/util/im/test_image.py
@@ -124,6 +124,24 @@ def test_force_2d(self):
         self.assertEqual(target_image.size, (6, 4))
         self.assertEqual(target_image.num_tiles, (3, 2))
 
+    def test_pad_tile(self):
+        a = np.arange(0, 6, dtype=np.float32)
+        a.shape = 2, 3
+        b = FastNdarrayDownsamplingImage.pad_tile(a, (3, 2))
+        np.testing.assert_equal(b, np.array([[0., 1., 2.],
+                                             [3., 4., 5.]]))
+        b = FastNdarrayDownsamplingImage.pad_tile(a, (4, 2))
+        np.testing.assert_equal(b, np.array([[0., 1., 2., np.nan],
+                                             [3., 4., 5., np.nan]]))
+        b = FastNdarrayDownsamplingImage.pad_tile(a, (3, 3))
+        np.testing.assert_equal(b, np.array([[0., 1., 2.],
+                                             [3., 4., 5.],
+                                             [np.nan, np.nan, np.nan]]))
+        b = FastNdarrayDownsamplingImage.pad_tile(a, (4, 3))
+        np.testing.assert_equal(b, np.array([[0., 1., 2., np.nan],
+                                             [3., 4., 5., np.nan],
+                                             [np.nan, np.nan, np.nan, np.nan]]))
+
 
 class ImagePyramidTest(TestCase):
     def test_create_from_image(self):