diff --git a/examples/helmholtz-dirichlet.py b/examples/helmholtz-dirichlet.py
index 22f8fa8a0083da62f1f17d7c79053056ce3ab33c..847e5c3fdfec588b6c8d3e10d2b31bb237f74022 100644
--- a/examples/helmholtz-dirichlet.py
+++ b/examples/helmholtz-dirichlet.py
@@ -96,8 +96,10 @@ def main():
 
     bdry_op_sym = (-loc_sign*0.5*sigma_sym
             + sqrt_w*(
-                alpha*sym.S(kernel, inv_sqrt_w_sigma, k=sym.var("k"))
-                - sym.D(kernel, inv_sqrt_w_sigma, k=sym.var("k"))
+                alpha*sym.S(kernel, inv_sqrt_w_sigma, k=sym.var("k"),
+                    qbx_forced_limit=+1)
+                - sym.D(kernel, inv_sqrt_w_sigma, k=sym.var("k"),
+                    qbx_forced_limit="avg")
                 ))
 
     # }}}
diff --git a/pytential/qbx/__init__.py b/pytential/qbx/__init__.py
index 869f92220f16817478375da3001e79f3c512b956..18b356be5c435dd0f5cc9ec14d12e18280b7b174 100644
--- a/pytential/qbx/__init__.py
+++ b/pytential/qbx/__init__.py
@@ -757,7 +757,7 @@ class QBXLayerPotentialSource(LayerPotentialSourceBase):
         if self.geometry_data_inspector is not None:
             perform_fmm = self.geometry_data_inspector(insn, bound_expr, geo_data)
             if not perform_fmm:
-                return [(o.name, 0) for o in insn.outputs], []
+                return [(o.name, 0) for o in insn.outputs]
 
         # }}}
 
@@ -780,7 +780,7 @@ class QBXLayerPotentialSource(LayerPotentialSourceBase):
                     (o.name,
                         all_potentials_on_every_tgt[o.kernel_index][tgt_slice]))
 
-        return result, []
+        return result
 
     # }}}
 
@@ -941,7 +941,7 @@ class QBXLayerPotentialSource(LayerPotentialSourceBase):
 
                 result.append((o.name, output_for_each_kernel[o.kernel_index]))
 
-        return result, []
+        return result
 
     # }}}
 
diff --git a/pytential/source.py b/pytential/source.py
index 6420494e77ba57c6f94288babc37783f142d8b4b..a8d0cba52feee0c4fb5fb3ccf7080d2cb45a7e4c 100644
--- a/pytential/source.py
+++ b/pytential/source.py
@@ -134,7 +134,7 @@ class PointPotentialSource(PotentialSource):
 
             result.append((o.name, output_for_each_kernel[o.kernel_index]))
 
-        return result, []
+        return result
 
     @memoize_method
     def weights_and_area_elements(self):
@@ -268,3 +268,5 @@ class LayerPotentialSourceBase(PotentialSource):
     # }}}
 
 # }}}
+
+# vim: foldmethod=marker
diff --git a/pytential/symbolic/compiler.py b/pytential/symbolic/compiler.py
index 17d23ebfe1683362615ac5e30968c5ea7dc3a594..456044e75a3903b08ffdfa6537f1fac0cd1f6e09 100644
--- a/pytential/symbolic/compiler.py
+++ b/pytential/symbolic/compiler.py
@@ -315,7 +315,7 @@ class Code(object):
 
         return "\n".join(lines)
 
-    # {{{ dynamic scheduler (generates static schedules by self-observation)
+    # {{{ dynamic scheduler
 
     class NoInstructionAvailable(Exception):
         pass
@@ -372,38 +372,35 @@ class Code(object):
         done_insns = set()
 
         while True:
-            insn = None
             discardable_vars = []
+            insn = None
 
-            # pick the next insn
-            if insn is None:
-                try:
-                    insn, discardable_vars = self.get_next_step(
-                            frozenset(list(context.keys())),
-                            frozenset(done_insns))
+            try:
+                insn, discardable_vars = self.get_next_step(
+                        frozenset(list(context.keys())),
+                        frozenset(done_insns))
 
-                except self.NoInstructionAvailable:
-                    # no available instructions: we're done
-                    break
-                else:
-                    for name in discardable_vars:
-                        del context[name]
+            except self.NoInstructionAvailable:
+                # no available instructions: we're done
+                break
+            else:
+                for name in discardable_vars:
+                    del context[name]
 
-                    done_insns.add(insn)
-                    assignments, new_futures = (
-                            insn.get_exec_function(exec_mapper)
-                            (exec_mapper.queue, insn, exec_mapper.bound_expr,
-                                exec_mapper))
+                done_insns.add(insn)
+                assignments = (
+                        insn.get_exec_function(exec_mapper)
+                        (exec_mapper.queue, insn, exec_mapper.bound_expr,
+                            exec_mapper))
 
-            if insn is not None:
+                assignees = insn.get_assignees()
                 for target, value in assignments:
                     if pre_assign_check is not None:
                         pre_assign_check(target, value)
 
+                    assert target in assignees
                     context[target] = value
 
-                assert not new_futures
-
         if len(done_insns) < len(self.instructions):
             print("Unreachable instructions:")
             for insn in set(self.instructions) - done_insns:
diff --git a/pytential/symbolic/execution.py b/pytential/symbolic/execution.py
index f658a6aa7c25cd3e0dc31caf0a702cbd591df88d..45840de2701898e6de8336d7d25792e9360d8d22 100644
--- a/pytential/symbolic/execution.py
+++ b/pytential/symbolic/execution.py
@@ -173,7 +173,7 @@ class EvaluationMapper(EvaluationMapperBase):
 
     def exec_assign(self, queue, insn, bound_expr, evaluate):
         return [(name, evaluate(expr))
-                for name, expr in zip(insn.names, insn.exprs)], []
+                for name, expr in zip(insn.names, insn.exprs)]
 
     # {{{ functions
 
diff --git a/pytential/unregularized.py b/pytential/unregularized.py
index b0d9926a4b8aedc7fb14a8ab4fe1531aeff743f9..e7fe1b3e73bfe17e14ab9aa6d57a86f6c9c92375 100644
--- a/pytential/unregularized.py
+++ b/pytential/unregularized.py
@@ -187,7 +187,7 @@ class UnregularizedLayerPotentialSource(LayerPotentialSourceBase):
 
             result.append((o.name, output_for_each_kernel[o.kernel_index]))
 
-        return result, []
+        return result
 
     # {{{ fmm-based execution
 
@@ -288,7 +288,7 @@ class UnregularizedLayerPotentialSource(LayerPotentialSourceBase):
 
         # }}}
 
-        return result, []
+        return result
 
     # }}}