diff --git a/devito/ir/clusters/cluster.py b/devito/ir/clusters/cluster.py
index 2143331aba..e7354b8693 100644
--- a/devito/ir/clusters/cluster.py
+++ b/devito/ir/clusters/cluster.py
@@ -231,17 +231,10 @@ def is_dense(self):
     @cached_property
     def is_sparse(self):
         """
-        A cluster is sparse if it represent a sparse operation i.e if both
-
-            * The cluster contains sparse functions
-            * The cluster uses dense functions
-
-        If only the first case is true, the cluster only contains operation on the sparse
-        function itself without indirection and therefore only contains dense operations.
+        A Cluster is sparse if it represents a sparse operation, i.e iff
+        There's at least one irregular access.
         """
-        return (any(f.is_SparseFunction for f in self.functions) and
-                len([f for f in self.functions
-                     if (f.is_Function and not f.is_SparseFunction)]) > 0)
+        return any(a.is_irregular for a in self.scope.accesses)
 
     @property
     def is_halo_touch(self):
diff --git a/tests/test_lower_clusters.py b/tests/test_lower_clusters.py
new file mode 100644
index 0000000000..f5ecf46bc6
--- /dev/null
+++ b/tests/test_lower_clusters.py
@@ -0,0 +1,18 @@
+from devito import Grid, SparseTimeFunction, TimeFunction, Operator
+from devito.ir.iet import FindSymbols
+
+
+class TestLowerReductions(object):
+
+    def test_no_temp_upon_reduce_expansion(self):
+        grid = Grid(shape=(10, 10, 10))
+
+        u = TimeFunction(name='u', grid=grid)
+        sf = SparseTimeFunction(name='sf', grid=grid, npoint=1, nt=5)
+
+        rec_term = sf.interpolate(expr=u)
+
+        op = Operator(rec_term, opt=('advanced', {'mapify-reduce': True}))
+
+        arrays = [i for i in FindSymbols().visit(op) if i.is_Array]
+        assert len([i for i in arrays if i.ndim == grid.dim]) == 0