diff --git a/compiler/par_conj_gen.m b/compiler/par_conj_gen.m
index 5aff96b1c..2ef270d1c 100644
--- a/compiler/par_conj_gen.m
+++ b/compiler/par_conj_gen.m
@@ -457,24 +457,23 @@ copy_slots_to_child_stack(FrameSize, LCVarLocn, LCSVarLocn, StackSlots,
         unexpected($module, $pred, "cannot convert to string")
     ),
 
-    BaseVarName = "BaseSp",
     FirstLine = "{\n",
-    DeclLine = string.format("\tMR_Word *%s;\n", [s(BaseVarName)]),
-    AssignLine = string.format("\t%s = MR_lc_child_stack_sp(%s, %s, %d);\n",
-        [s(BaseVarName), s(LCVarName), s(LCSVarName), i(FrameSize)]),
-    list.map(copy_one_slot_to_child_stack(BaseVarName),
+    IncrLine = string.format("\tMR_lc_inc_worker_sp(%s, %s, %d);\n",
+        [s(LCVarName), s(LCSVarName), i(FrameSize)]),
+    list.map(copy_one_slot_to_child_stack(LCVarName, LCSVarName),
         StackSlots, CopyStrs),
     string.append_list(CopyStrs, CopyLines),
     LastLine = "\t}\n",
-    CodeStr = FirstLine ++ DeclLine ++ AssignLine ++ CopyLines ++ LastLine.
+    CodeStr = FirstLine ++ IncrLine ++ CopyLines ++ LastLine.
 
-:- pred copy_one_slot_to_child_stack(string::in, lval::in, string::out) is det.
+:- pred copy_one_slot_to_child_stack(string::in, string::in, lval::in,
+    string::out) is det.
 
-copy_one_slot_to_child_stack(BaseVarName, StackSlot, CopyStr) :-
+copy_one_slot_to_child_stack(LCVarName, LCSVarName, StackSlot, CopyStr) :-
     ( StackSlotName = lval_to_string(StackSlot) ->
         ( StackSlot = stackvar(N) ->
-            CopyStr = string.format("\tMR_based_stackvar(%s, %d) = %s;\n",
-                [s(BaseVarName), i(N), s(StackSlotName)])
+            CopyStr = string.format("\tMR_lc_worker_sv(%s, %s, %d) = %s;\n",
+                [s(LCVarName), s(LCSVarName), i(N), s(StackSlotName)])
         ;
             unexpected($module, $pred, "not stack slot")
         )
diff --git a/runtime/mercury_par_builtin.h b/runtime/mercury_par_builtin.h
index a12af6a8c..5a45543fe 100644
--- a/runtime/mercury_par_builtin.h
+++ b/runtime/mercury_par_builtin.h
@@ -530,15 +530,16 @@ extern MR_Bool MR_lc_try_get_free_slot(MR_LoopControl *lc,
     do {                                                                    \
         MR_Context *ctxt;                                                   \
                                                                             \
-        ctxt = (lc)->MR_lc_slots[lcs_idx].MR_lcs_context;                   \
-        MR_lcs_context->MR_ctxt_sp += N;                                    \
+        ctxt = ((MR_LoopControl*)lc)->MR_lc_slots[lcs_idx].MR_lcs_context;  \
+        ctxt->MR_ctxt_sp += N;                                              \
     } while (0);
 
 /*
 ** Access a slot on the stack of the worker context in the loop control slot.
 */
 #define MR_lc_worker_sv(lc, lcs_idx, N)                                     \
-  MR_based_stackvar((lc)->MR_lc_slots[lc_idx].MR_lcs_context->MR_ctxt_sp, (N))
+  MR_based_stackvar(((MR_LoopControl*)lc)->MR_lc_slots[lcs_idx].            \
+    MR_lcs_context->MR_ctxt_sp, (N))
 
 /*
 ** Try to spawn off this code using the free slot.