Index: engine/builtins.c
===================================================================
--- engine/builtins.c	(revision 75605)
+++ engine/builtins.c	(working copy)
@@ -2114,9 +2114,12 @@
 PyObject * bjam_backtrace( PyObject * self, PyObject * args )
 {
     PyObject     * result = PyList_New( 0 );
-    struct frame * f = frame_before_python_call;
+    struct frame * f = frame_before_python_call();
+    
+    if ( f )
+        f = f->prev
 
-    for ( ; f = f->prev; )
+    for ( ; f; f = f->prev )
     {
         PyObject * tuple = PyTuple_New( 4 );
         char     * file;
@@ -2140,9 +2143,10 @@
 
 PyObject * bjam_caller( PyObject * self, PyObject * args )
 {
-    if ( !frame_before_python_call )
+    struct frame * f = frame_before_python_call();
+    if ( !f )
         Py_RETURN_NONE;
-    return PyString_FromString(frame_before_python_call->prev->module->name);
+    return PyString_FromString(f->prev->module->name);
 }
 
 #endif  /* #ifdef HAVE_PYTHON */
Index: engine/compile.c
===================================================================
--- engine/compile.c	(revision 75605)
+++ engine/compile.c	(working copy)
@@ -93,8 +93,28 @@
 void backtrace_line( FRAME *frame );
 void print_source_line( PARSE* p );
 
-struct frame * frame_before_python_call;
+#define MAX_FRAME_STACK_DEPTH 20
+static struct frame * frame_stack[ MAX_FRAME_STACK_DEPTH ];
+static unsigned int frame_depth;
 
+static push_frame( struct frame * param )
+{
+    assert( frame_depth < MAX_FRAME_STACK_DEPTH );
+    frame_stack[ frame_depth ] = param;
+    frame_depth++;
+}
+
+static pop_frame()
+{
+    assert( frame_depth > 0 );
+    frame_depth--;
+}
+
+struct frame * frame_before_python_call()
+{
+    return frame_depth > 0 ? frame_stack[ frame_depth - 1 ] : 0;
+}
+
 void frame_init( FRAME* frame )
 {
     frame->prev = 0;
@@ -863,9 +883,9 @@
         }
     }
 
-    frame_before_python_call = frame;
+    push_frame( frame );
     py_result = PyObject_Call( r->python_function, arguments, kw );
-    frame_before_python_call = NULL;
+    pop_frame();
     Py_DECREF(arguments);
     Py_XDECREF(kw);
     if ( py_result != NULL )
Index: engine/frames.h
===================================================================
--- engine/frames.h	(revision 75605)
+++ engine/frames.h	(working copy)
@@ -29,7 +29,7 @@
  * is not defined. Further, if Jam calls Python which calls Jam and so on, this
  * variable only keeps the most recent Jam frame.
  */
-extern struct frame * frame_before_python_call;
+struct frame * frame_before_python_call();
 
 void frame_init( FRAME * );  /* implemented in compile.c */
 void frame_free( FRAME * );  /* implemented in compile.c */