diff --git a/Cargo.toml b/Cargo.toml
index 68214c2..ffb03fb 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -22,9 +22,9 @@ edition = "2021"
 repository = "https://github.com/mtshiba/pylyzer"
 
 [workspace.dependencies]
-erg_common = { version = "0.6.40-nightly.1", features = ["py_compat", "els"] }
-erg_compiler = { version = "0.6.40-nightly.1", features = ["py_compat", "els"] }
-els = { version = "0.1.52-nightly.1", features = ["py_compat"] }
+erg_common = { version = "0.6.40", features = ["py_compat", "els"] }
+erg_compiler = { version = "0.6.40", features = ["py_compat", "els"] }
+els = { version = "0.1.52", features = ["py_compat"] }
 # rustpython-parser = { version = "0.3.0", features = ["all-nodes-with-ranges", "location"] }
 # rustpython-ast = { version = "0.3.0", features = ["all-nodes-with-ranges", "location"] }
 rustpython-parser = { git = "https://github.com/RustPython/Parser", version = "0.3.1", features = ["all-nodes-with-ranges", "location"] }
diff --git a/crates/py2erg/gen_decl.rs b/crates/py2erg/gen_decl.rs
index c4226a4..cab06da 100644
--- a/crates/py2erg/gen_decl.rs
+++ b/crates/py2erg/gen_decl.rs
@@ -65,6 +65,14 @@ impl DeclFileGenerator {
         }
     }
 
+    // e.g. `x: foo.Bar` => `foo = pyimport "foo"; x: foo.Bar`
+    fn prepare_using_type(&mut self, typ: &Type) {
+        let namespace = Str::rc(typ.namespace().split('.').next().unwrap());
+        if !namespace.is_empty() && self.imported.insert(namespace.clone()) {
+            self.code += &format!("{namespace} = pyimport \"{namespace}\"\n");
+        }
+    }
+
     fn gen_chunk_decl(&mut self, chunk: &Expr) {
         match chunk {
             Expr::Def(def) => {
@@ -75,6 +83,7 @@ impl DeclFileGenerator {
                     .replace('\0', "")
                     .replace(['%', '*'], "___");
                 let ref_t = def.sig.ident().ref_t();
+                self.prepare_using_type(ref_t);
                 let typ = escape_type(ref_t.replace_failure().to_string_unabbreviated());
                 // Erg can automatically import nested modules
                 // `import http.client` => `http = pyimport "http"`
@@ -119,6 +128,7 @@ impl DeclFileGenerator {
                         .typ()
                         .replace_failure()
                         .to_string_unabbreviated();
+                    self.prepare_using_type(class.sup.typ());
                     let sup = escape_type(sup);
                     let decl = format!(".{class_name} <: {sup}\n");
                     self.code += &decl;
@@ -129,6 +139,7 @@ impl DeclFileGenerator {
                 }) = def.obj.base_or_sup()
                 {
                     for (attr, t) in rec.iter() {
+                        self.prepare_using_type(t);
                         let typ = escape_type(t.replace_failure().to_string_unabbreviated());
                         let decl = format!("{}.{}: {typ}\n", self.namespace, attr.symbol);
                         self.code += &decl;
@@ -140,6 +151,7 @@ impl DeclFileGenerator {
                 }) = def.obj.additional()
                 {
                     for (attr, t) in rec.iter() {
+                        self.prepare_using_type(t);
                         let typ = escape_type(t.replace_failure().to_string_unabbreviated());
                         let decl = format!("{}.{}: {typ}\n", self.namespace, attr.symbol);
                         self.code += &decl;
diff --git a/tests/foo/__init__.py b/tests/foo/__init__.py
index 98d94b6..d231887 100644
--- a/tests/foo/__init__.py
+++ b/tests/foo/__init__.py
@@ -1,4 +1,4 @@
-from .bar import i, Bar
+from .bar import i, Bar, Baz, Qux
 
 from . import bar
 from . import baz
diff --git a/tests/foo/bar.py b/tests/foo/bar.py
index 0fbe907..5c1d692 100644
--- a/tests/foo/bar.py
+++ b/tests/foo/bar.py
@@ -2,3 +2,9 @@
 
 class Bar:
     def f(self): return 1
+
+class Baz(Exception):
+    pass
+
+class Qux(Baz):
+    pass
diff --git a/tests/import.py b/tests/import.py
index 500582d..11228de 100644
--- a/tests/import.py
+++ b/tests/import.py
@@ -41,3 +41,5 @@
 
 Resp = http.client.HTTPResponse
 assert export.http.client.HTTPResponse == Resp
+
+_ = bar.Baz