diff --git a/src/library/kernel_bindings.cpp b/src/library/kernel_bindings.cpp
index 22accf2ae..3ec2eb04a 100644
--- a/src/library/kernel_bindings.cpp
+++ b/src/library/kernel_bindings.cpp
@@ -43,6 +43,7 @@ Author: Leonardo de Moura
 namespace lean {
 static environment get_global_environment(lua_State * L);
 io_state * get_io_state(lua_State * L);
+io_state get_tmp_io_state(lua_State * L);
 
 // Level
 DECL_UDATA(level)
@@ -1161,9 +1162,16 @@ static int import_modules(environment const & env, lua_State * L, int s) {
     buffer<std::string> mnames;
     to_string_buffer(L, s, mnames);
     unsigned num_threads = 1;
-    if (lua_gettop(L) > s)
+    int nargs = lua_gettop(L);
+    if (nargs > s)
         num_threads = lua_tonumber(L, s+1);
-    return push_environment(L, import_modules(env, mnames.size(), mnames.data(), num_threads));
+
+    if (nargs > s + 1 && is_io_state(L, s+2))
+        return push_environment(L, import_modules(env, mnames.size(), mnames.data(), num_threads, to_io_state(L, s+2)));
+    else if (io_state * ios = get_io_state(L))
+        return push_environment(L, import_modules(env, mnames.size(), mnames.data(), num_threads, *ios));
+    else
+        return push_environment(L, import_modules(env, mnames.size(), mnames.data(), num_threads, get_tmp_io_state(L)));
 }
 
 static int import_modules(lua_State * L) {
@@ -1397,6 +1405,10 @@ io_state * get_io_state(lua_State * L) {
     return nullptr;
 }
 
+io_state get_tmp_io_state(lua_State * L) {
+    return io_state(get_global_options(L), get_global_formatter(L));
+}
+
 // Justification
 DECL_UDATA(justification)
 
diff --git a/src/library/module.cpp b/src/library/module.cpp
index da06892fa..67cef1fe0 100644
--- a/src/library/module.cpp
+++ b/src/library/module.cpp
@@ -142,6 +142,7 @@ struct import_modules_fn {
     typedef std::tuple<module_idx, unsigned, delayed_update_fn> delayed_update;
     shared_environment             m_senv;
     unsigned                       m_num_threads;
+    io_state                       m_ios;
     mutex                          m_asynch_mutex;
     condition_variable             m_asynch_cv;
     std::vector<asynch_update_fn>  m_asynch_tasks;
@@ -162,8 +163,8 @@ struct import_modules_fn {
     typedef std::shared_ptr<module_info> module_info_ptr;
     std::unordered_map<std::string, module_info_ptr> m_module_info;
 
-    import_modules_fn(environment const & env, unsigned num_threads):
-        m_senv(env), m_num_threads(num_threads),
+    import_modules_fn(environment const & env, unsigned num_threads, io_state const & ios):
+        m_senv(env), m_num_threads(num_threads), m_ios(ios),
         m_import_counter(0), m_all_modules_imported(false) {
         if (m_num_threads == 0)
             m_num_threads = 1;
@@ -343,7 +344,7 @@ struct import_modules_fn {
                           return std::get<1>(u1) < std::get<1>(u2);
                   });
         for (auto const & d : m_delayed_tasks) {
-            env = std::get<2>(d)(env);
+            env = std::get<2>(d)(env, m_ios);
         }
         return env;
     }
@@ -366,11 +367,13 @@ struct import_modules_fn {
     }
 };
 
-environment import_modules(environment const & env, unsigned num_modules, std::string const * modules, unsigned num_threads) {
-    return import_modules_fn(env, num_threads)(num_modules, modules);
+environment import_modules(environment const & env, unsigned num_modules, std::string const * modules,
+                           unsigned num_threads, io_state const & ios) {
+    return import_modules_fn(env, num_threads, ios)(num_modules, modules);
 }
 
-environment import_module(environment const & env, std::string const & module, unsigned num_threads) {
-    return import_modules(env, 1, &module, num_threads);
+environment import_module(environment const & env, std::string const & module,
+                          unsigned num_threads, io_state const & ios) {
+    return import_modules(env, 1, &module, num_threads, ios);
 }
 }
diff --git a/src/library/module.h b/src/library/module.h
index 0ee5ae25a..13f9fb552 100644
--- a/src/library/module.h
+++ b/src/library/module.h
@@ -9,6 +9,7 @@ Author: Leonardo de Moura
 #include <iostream>
 #include "util/serializer.h"
 #include "library/shared_environment.h"
+#include "library/io_state.h"
 
 namespace lean {
 /**
@@ -16,8 +17,10 @@ namespace lean {
    Modules included directly or indirectly by them are also imported.
    The environment \c env is usually an empty environment.
 */
-environment import_modules(environment const & env, unsigned num_modules, std::string const * modules, unsigned num_threads = 1);
-environment import_module(environment const & env, std::string const & module, unsigned num_threads = 1);
+environment import_modules(environment const & env, unsigned num_modules, std::string const * modules,
+                           unsigned num_threads, io_state const & ios);
+environment import_module(environment const & env, std::string const & module,
+                          unsigned num_threads, io_state const & ios);
 
 /**
    \brief Store/Export module using \c env to the output stream \c out.
@@ -32,8 +35,7 @@ typedef std::function<void(shared_environment & env)> asynch_update_fn;
     Example: if module A was imported before B, then delayed updates from A
     are executed before the ones from B.
 */
-typedef std::function<environment(environment const & env)> delayed_update_fn;
-
+typedef std::function<environment(environment const & env, io_state const & ios)> delayed_update_fn;
 
 /**
    \brief A reader for importing data from a stream using deserializer \c d.