diff --git a/child.mod b/child.mod
index 96382e6..db3b79c 100644
--- a/child.mod
+++ b/child.mod
@@ -13,14 +13,24 @@
  }
  
  VERBATIM
- static subtree(sec, sym) Section* sec; Symbol* sym; {
+ /* NEURON >= 9: Section is incomplete in MOD translation units; use accessors.
+    NEURON < 9: full Section definition is available (section.h). */
+ #if NRN_VERSION_GTEQ(9, 0, 0)
+ #define SEC_CHILD(s)   _nrn_mechanism_get_child(s)
+ #define SEC_SIBLING(s) _nrn_mechanism_get_sibling(s)
+ #else
+ #define SEC_CHILD(s)   ((s)->child)
+ #define SEC_SIBLING(s) ((s)->sibling)
+ #endif
+ 
+ static void subtree(Section* sec, Symbol* sym) {
  	Section* child;
  
  	nrn_pushsec(sec);	/* move these three (sec becomes child) */
  	hoc_run_stmt(sym);	/* into the loop to do only the first level */
  	nrn_popsec();
  
- 	for (child = sec->child; child; child = child->sibling) {
+ 	for (child = SEC_CHILD(sec); child; child = SEC_SIBLING(child)) {
  		subtree(child, sym);
  	}
  }
@@ -29,8 +39,8 @@
  PROCEDURE subtree_traverse_all() {
    VERBATIM
    {
- 	Section* chk_access();
- 	Symbol* hoc_parse_stmt();
+ 	/* Do not redeclare chk_access / hoc_parse_stmt here: in C++ (NEURON 9+)
+ 	   a local Symbol* hoc_parse_stmt(); is a zero-arg overload that hides the real API. */
  	Symlist* symlist = (Symlist*)0;
  	subtree(chk_access(), hoc_parse_stmt(gargstr(1), &symlist));
  	/* if following not executed (ie hoc error in statement),
@@ -38,4 +48,4 @@
  	hoc_free_list(&symlist);
    }
    ENDVERBATIM
- }
\ No newline at end of file
+ }
diff --git a/childa.mod b/childa.mod
index ca45638..d39c41c 100644
--- a/childa.mod
+++ b/childa.mod
@@ -13,12 +13,20 @@ NEURON {
 }
 
 VERBATIM
-static subtree(sec, sym) Section* sec; Symbol* sym; {
+/* NEURON >= 9: Section is incomplete in MOD translation units; use accessors.
+   NEURON < 9: full Section definition is available (section.h). */
+#if NRN_VERSION_GTEQ(9, 0, 0)
+#define SEC_CHILD(s)   _nrn_mechanism_get_child(s)
+#define SEC_SIBLING(s) _nrn_mechanism_get_sibling(s)
+#else
+#define SEC_CHILD(s)   ((s)->child)
+#define SEC_SIBLING(s) ((s)->sibling)
+#endif
+
+static void subtree(Section* sec, Symbol* sym) {
         Section* child;
 
- 
-
-        for (child = sec->child; child; child = child->sibling) {
+        for (child = SEC_CHILD(sec); child; child = SEC_SIBLING(child)) {
        nrn_pushsec(child);       /* move these three (sec becomes child) */
         hoc_run_stmt(sym);      /* into the loop to do only the first level */
         nrn_popsec(); 
@@ -30,8 +38,8 @@ ENDVERBATIM
 PROCEDURE subtree_traverse() {
   VERBATIM
   {
-        Section* chk_access();
-        Symbol* hoc_parse_stmt();
+        /* Do not redeclare chk_access / hoc_parse_stmt here: in C++ (NEURON 9+)
+           a local Symbol* hoc_parse_stmt(); is a zero-arg overload that hides the real API. */
         Symlist* symlist = (Symlist*)0;
         subtree(chk_access(), hoc_parse_stmt(gargstr(1), &symlist));
         /* if following not executed (ie hoc error in statement),