diff --git a/zipline/pipeline/engine.py b/zipline/pipeline/engine.py
index ba5485bc..a8347776 100644
--- a/zipline/pipeline/engine.py
+++ b/zipline/pipeline/engine.py
@@ -236,17 +236,10 @@ class SimplePipelineEngine(object):
         """
         Load mask and mask row labels for term.
         """
-        mask = term.mask
+        mask = term.mask if not term.atomic else self._root_mask_term
         offset = graph.extra_rows[mask] - graph.extra_rows[term]
         return workspace[mask][offset:], dates[offset:]
 
-    def _mask_and_dates_for_atomic_terms(self, terms, workspace, graph, dates):
-        max_extra_rows = max(graph.extra_rows[term] for term in terms)
-
-        mask = self._root_mask_term
-        offset = graph.extra_rows[mask] - max_extra_rows
-        return workspace[mask][offset:], dates[offset:]
-
     @staticmethod
     def _inputs_for_term(term, workspace, graph):
         """
@@ -281,10 +274,14 @@ class SimplePipelineEngine(object):
             out.append(input_data)
         return out
 
-    def _atomic_terms_for_loader(self, graph, loader):
+    def _similar_atomic_terms(self, graph, atomic_term):
         loader_dispatch = self.loader_dispatch
+        loader = loader_dispatch(atomic_term)
+        extra_rows = graph.extra_rows[atomic_term]
+
         for term in graph.atomic_terms:
-            if loader_dispatch(term) == loader:
+            if (loader_dispatch(term) == loader
+                    and graph.extra_rows[term] == extra_rows):
                 yield term
 
     def loader_dispatch(self, term):
@@ -333,13 +330,18 @@ class SimplePipelineEngine(object):
             if term in workspace:
                 continue
 
+            # Asset labels are always the same, but date labels vary by how
+            # many extra rows are needed.
+            mask, mask_dates = self._mask_and_dates_for_term(
+                term, workspace, graph, dates
+            )
+
             if term.atomic:
-                loader = loader_dispatch(term)
-                to_load = sorted(self._atomic_terms_for_loader(graph, loader),
-                                 key=lambda t: t.dataset)
-                mask, mask_dates = self._mask_and_dates_for_atomic_terms(
-                    to_load, workspace, graph, dates,
+                to_load = sorted(
+                    self._similar_atomic_terms(graph, term),
+                    key=lambda t: t.dataset
                 )
+                loader = loader_dispatch(term)
                 loaded = loader.load_adjusted_array(
                     to_load, mask_dates, assets, mask,
                 )
@@ -347,11 +349,6 @@ class SimplePipelineEngine(object):
                 for loaded_term, adj_array in zip_longest(to_load, loaded):
                     workspace[loaded_term] = adj_array
             else:
-                # Asset labels are always the same, but date labels vary by how
-                # many extra rows are needed.
-                mask, mask_dates = self._mask_and_dates_for_term(
-                    term, workspace, graph, dates
-                )
                 workspace[term] = term._compute(
                     self._inputs_for_term(term, workspace, graph),
                     mask_dates,