diff --git a/Python/compile.c b/Python/compile.c
index b256198..35ec10a 100644
--- a/Python/compile.c
+++ b/Python/compile.c
@@ -652,11 +652,16 @@
 	return b->b_iused++;
 }
 
-/* Set the i_lineno member of the instruction at offse off if the
-   line number for the current expression/statement (?) has not
+/* Set the i_lineno member of the instruction at offset off if the
+   line number for the current expression/statement has not
    already been set.  If it has been set, the call has no effect.
 
-   Every time a new node is b
+   The line number is reset in the following cases:
+   - when entering a new scope
+   - on each statement
+   - on each expression that start a new line
+   - before the "except" clause
+   - before the "for" and "while" expressions
 */
 
 static void
@@ -1750,9 +1755,8 @@
 	VISIT(c, expr, s->v.For.iter);
 	ADDOP(c, GET_ITER);
 	compiler_use_next_block(c, start);
-	/* XXX(nnorwitz): is there a better way to handle this?
-	   for loops are special, we want to be able to trace them
-	   each time around, so we need to set an extra line number. */
+	/* for expressions must be traced on each iteration,
+	   so we need to set an extra line number. */
 	c->u->u_lineno_set = 0;
 	ADDOP_JREL(c, FOR_ITER, cleanup);
 	VISIT(c, expr, s->v.For.target);
@@ -1799,6 +1803,9 @@
 	if (!compiler_push_fblock(c, LOOP, loop))
 		return 0;
 	if (constant == -1) {
+		/* while expressions must be traced on each iteration,
+		   so we need to set an extra line number. */
+		c->u->u_lineno_set = 0;
 		VISIT(c, expr, s->v.While.test);
 		ADDOP_JREL(c, JUMP_IF_FALSE, anchor);
 		ADDOP(c, POP_TOP);
@@ -1979,8 +1986,8 @@
 						s->v.TryExcept.handlers, i);
 		if (!handler->type && i < n-1)
 		    return compiler_error(c, "default 'except:' must be last");
-	c->u->u_lineno_set = 0;
-	c->u->u_lineno = handler->lineno;
+		c->u->u_lineno_set = 0;
+		c->u->u_lineno = handler->lineno;
 		except = compiler_new_block(c);
 		if (except == NULL)
 			return 0;
@@ -3762,10 +3769,7 @@
 	assert(d_bytecode >= 0);
 	assert(d_lineno >= 0);
 
-	/* XXX(nnorwitz): is there a better way to handle this?
-	   for loops are special, we want to be able to trace them
-	   each time around, so we need to set an extra line number. */
-	if (d_lineno == 0 && i->i_opcode != FOR_ITER)
+	if(d_bytecode == 0 && d_lineno == 0)
 		return 1;
 
 	if (d_bytecode > 255) {