diff --git a/loopy/codegen/loop.py b/loopy/codegen/loop.py
index 81686878d55ddebc49f2122d473eb8fcf8d2ec32..ad80475c1d27f67b3df8a885f60dd96ff28efe6a 100644
--- a/loopy/codegen/loop.py
+++ b/loopy/codegen/loop.py
@@ -410,12 +410,17 @@ def generate_sequential_loop_dim_code(codegen_state, sched_index):
 
         # {{{ find implemented loop, build inner code
 
-        from loopy.isl_helpers import make_loop_bounds_from_pwaffs
+        from loopy.symbolic import pw_aff_to_pw_aff_implemented_by_expr
+        impl_lbound = pw_aff_to_pw_aff_implemented_by_expr(lbound)
+        impl_ubound = pw_aff_to_pw_aff_implemented_by_expr(ubound)
 
         # impl_loop may be overapproximated
+        from loopy.isl_helpers import make_loop_bounds_from_pwaffs
         impl_loop = make_loop_bounds_from_pwaffs(
                 dom_and_slab.space,
-                loop_iname, lbound, ubound)
+                loop_iname,
+                impl_lbound,
+                impl_ubound)
 
         for iname in moved_inames:
             dt, idx = impl_loop.get_var_dict()[iname]
diff --git a/loopy/symbolic.py b/loopy/symbolic.py
index 430c651589939a1001432bd8db413cb5902b14a6..52fd6e57f92e7f9599a3a0fb4256f97347708303 100644
--- a/loopy/symbolic.py
+++ b/loopy/symbolic.py
@@ -1150,6 +1150,23 @@ def pw_aff_to_expr(pw_aff, int_ok=False):
 
     return expr
 
+
+def pw_aff_to_pw_aff_implemented_by_expr(pw_aff):
+    pieces = pw_aff.get_pieces()
+
+    rest = isl.Set.universe(pw_aff.space.params())
+    aff_set, aff = pieces[0]
+    impl_pw_aff = isl.PwAff.alloc(aff_set, aff)
+    rest = rest.intersect_params(aff_set.complement())
+
+    for aff_set, aff in pieces[1:-1]:
+        impl_pw_aff = impl_pw_aff.union_max(
+            isl.PwAff.alloc(aff_set, aff))
+        rest = rest.intersect_params(aff_set.complement())
+
+    _, aff = pieces[-1]
+    return impl_pw_aff.union_max(isl.PwAff.alloc(rest, aff)).coalesce()
+
 # }}}