diff --git a/loopy/symbolic.py b/loopy/symbolic.py
index 0cc8f4ba6a1531d748bd90492f570dbb563d962d..8927cd6fba97d847e425fe9b2eaa8960297cdb76 100644
--- a/loopy/symbolic.py
+++ b/loopy/symbolic.py
@@ -57,6 +57,8 @@ from pymbolic.mapper.constant_folder import \
 
 from pymbolic.parser import Parser as ParserBase
 
+from loopy.diagnostic import ExpressionToAffineConversionError
+
 import islpy as isl
 from islpy import dim_type
 
@@ -1401,16 +1403,9 @@ def simplify_using_aff(kernel, expr):
 
     domain = kernel.get_inames_domain(inames)
 
-    from pymbolic.mapper.evaluator import UnknownVariableError
-
     try:
-        with isl.SuppressedWarnings(kernel.isl_context):
-            aff = aff_from_expr(domain.space, expr)
-    except isl.Error:
-        return expr
-    except TypeError:
-        return expr
-    except UnknownVariableError:
+        aff = guarded_aff_from_expr(domain.space, expr)
+    except ExpressionToAffineConversionError:
         return expr
 
     # FIXME: Deal with assumptions, too.
diff --git a/loopy/transform/array_buffer_map.py b/loopy/transform/array_buffer_map.py
index 618e36f20da8b3f9089ecf5ce88d6b3177528570..b62e13d6b268a9b84e209a5c8958dc949114eecf 100644
--- a/loopy/transform/array_buffer_map.py
+++ b/loopy/transform/array_buffer_map.py
@@ -1,5 +1,4 @@
 from __future__ import division, absolute_import
-from six.moves import range, zip
 
 __copyright__ = "Copyright (C) 2012-2015 Andreas Kloeckner"
 
@@ -23,6 +22,8 @@ OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
 THE SOFTWARE.
 """
 
+from six.moves import range, zip
+
 import islpy as isl
 from islpy import dim_type
 from loopy.symbolic import (get_dependencies, SubstitutionMapper)
@@ -89,12 +90,12 @@ def build_per_access_storage_to_domain_map(storage_axis_exprs, domain,
 
     stor2sweep = None
 
-    from loopy.symbolic import aff_from_expr
+    from loopy.symbolic import guarded_aff_from_expr
 
     for saxis, sa_expr in zip(storage_axis_names, storage_axis_exprs):
-        cns = isl.Constraint.equality_from_aff(
-                aff_from_expr(set_space,
-                    var(saxis+"'") - prime_sweep_inames(sa_expr)))
+        cns_expr = var(saxis+"'") - prime_sweep_inames(sa_expr)
+        cns_aff = guarded_aff_from_expr(set_space, cns_expr)
+        cns = isl.Constraint.equality_from_aff(cns_aff)
 
         cns_map = isl.BasicMap.from_constraint(cns)
         if stor2sweep is None:
@@ -352,13 +353,11 @@ class ArrayToBufferMap(object):
                 self.stor2sweep,
                 except_inames=frozenset(self.primed_sweep_inames)).domain()
 
-        arg_inames = (
-                set(global_s2s_par_dom.get_var_names(dim_type.param))
-                & self.kernel.all_inames())
+        arg_inames = set(global_s2s_par_dom.get_var_names(dim_type.param))
 
         for arg in storage_axis_exprs:
             arg_inames.update(get_dependencies(arg))
-        arg_inames = frozenset(arg_inames)
+        arg_inames = frozenset(arg_inames & self.kernel.all_inames())
 
         from loopy.kernel import CannotBranchDomainTree
         try:
diff --git a/test/test_apps.py b/test/test_apps.py
index 2a88e0b7400d5330d652f1fc5c2b1ba37d19df9f..e7f4004fa0f2285920bdf9a0848c0d400e2c31b7 100644
--- a/test/test_apps.py
+++ b/test/test_apps.py
@@ -43,6 +43,8 @@ else:
 from pyopencl.tools import pytest_generate_tests_for_pyopencl \
         as pytest_generate_tests
 
+from loopy.diagnostic import LoopyError
+
 __all__ = [
         "pytest_generate_tests",
         "cl"  # 'cl.create_some_context'
@@ -670,6 +672,26 @@ def test_domain_tree_nesting():
         assert depth(i) < 2
 
 
+def test_prefetch_through_indirect_access():
+    knl = lp.make_kernel("{[i, j, k]: 0 <= i,k < 10 and 0<=j<2}",
+        """
+        for i, j, k
+            a[map1[indirect[i], j], k] = 2
+        end
+        """,
+        [
+            lp.GlobalArg("a", strides=(2, 1), dtype=int),
+            lp.GlobalArg("map1", shape=(10, 10), dtype=int),
+            "..."
+            ],
+        target=lp.CTarget())
+
+    knl = lp.prioritize_loops(knl, "i,j,k")
+
+    with pytest.raises(LoopyError):
+        knl = lp.add_prefetch(knl, "map1[:, j]")
+
+
 if __name__ == "__main__":
     if len(sys.argv) > 1:
         exec(sys.argv[1])