3 files changed, 4 insertions, 2 deletions

diff --git a/README.md b/README.md
index 360c1e3..021ea3a 100644
--- a/README.md
+++ b/README.md
@@ -96,7 +96,7 @@ Control flow:
 Procedures:
 
 - `procedure <ident>(<var>, ... ; <var>, ... ) begin <stm> end` declaration, first argument list are value arguments (vars passed to procedure), second argument list are variable arguments (vars returned from procedure).
-- `<ident>(<var>, ... ; <var>, ... )` call
+- `<ident>(<aexpr>, ... ; <var>, ... )` call
 
 
 **Expression**
diff --git a/src/ast.c b/src/ast.c
index 9c13d79..eced7f3 100644
--- a/src/ast.c
+++ b/src/ast.c
@@ -246,4 +246,4 @@ void imp_ast_list_destroy(IMP_ASTNodeList *list) {
   imp_ast_destroy(list->node);
   imp_ast_list_destroy(list->next);
   free(list);
-}
\ No newline at end of file
+}
diff --git a/src/driver.c b/src/driver.c
index c43b899..d8cd143 100644
--- a/src/driver.c
+++ b/src/driver.c
@@ -20,6 +20,7 @@ int imp_driver_interpret_file (IMP_InterpreterContext *context, const char *path
   yyin = fopen(path, "r");
   if (!yyin) return -1;
   yyrestart(yyin);
+  ast_root = NULL;
   if (yyparse()) {
     imp_ast_destroy(ast_root);
     fclose(yyin);
@@ -37,6 +38,7 @@ int imp_driver_interpret_file (IMP_InterpreterContext *context, const char *path
 
 int imp_driver_interpret_str (IMP_InterpreterContext *context, const char *str) {
   YY_BUFFER_STATE buf = yy_scan_string(str);
+  ast_root = NULL;
   if (yyparse()) {
     imp_ast_destroy(ast_root);
     yy_delete_buffer(buf);