diff --git a/lib/typeprof/core/service.rb b/lib/typeprof/core/service.rb
index 11b9e068..a79ca1c0 100644
--- a/lib/typeprof/core/service.rb
+++ b/lib/typeprof/core/service.rb
@@ -203,11 +203,20 @@ def type_definitions(path, pos)
         if node.ret
           ty_defs = []
           node.ret.types.map do |ty, _source|
-            if ty.is_a?(Type::Instance)
-              ty.mod.module_decls.each do |mdecl|
-                # TODO
+            mod = case ty
+                  when Type::Instance, Type::Singleton
+                    ty.mod
+                  else
+                    base = ty.base_type(@genv)
+                    base.mod if base.is_a?(Type::Instance)
+                  end
+
+            if mod
+              mod.module_decls.each do |mdecl|
+                decl_path = mdecl.lenv.path
+                ty_defs << [decl_path, mdecl.code_range] if decl_path
               end
-              ty.mod.module_defs.each do |mdef_node|
+              mod.module_defs.each do |mdef_node|
                 ty_defs << [mdef_node.lenv.path, mdef_node.code_range]
               end
             end
diff --git a/test/fixtures/type_definition/sig/test.rbs b/test/fixtures/type_definition/sig/test.rbs
new file mode 100644
index 00000000..c9dbbe44
--- /dev/null
+++ b/test/fixtures/type_definition/sig/test.rbs
@@ -0,0 +1,2 @@
+class Foo
+end
diff --git a/test/fixtures/type_definition/test.rb b/test/fixtures/type_definition/test.rb
new file mode 100644
index 00000000..3f7fb90e
--- /dev/null
+++ b/test/fixtures/type_definition/test.rb
@@ -0,0 +1,5 @@
+class Foo
+end
+
+foo = Foo.new
+foo
diff --git a/test/fixtures/type_definition/typeprof.conf.json b/test/fixtures/type_definition/typeprof.conf.json
new file mode 100644
index 00000000..96fc8809
--- /dev/null
+++ b/test/fixtures/type_definition/typeprof.conf.json
@@ -0,0 +1,5 @@
+{
+  "typeprof_version": "experimental",
+  "analysis_unit_dirs": ["."],
+  "sig_dirs": ["sig"]
+}
diff --git a/test/lsp/lsp_test.rb b/test/lsp/lsp_test.rb
index 782fc1ba..5ef58ec7 100644
--- a/test/lsp/lsp_test.rb
+++ b/test/lsp/lsp_test.rb
@@ -285,6 +285,78 @@ def test(x)
       end
     end
 
-    # TODO: add a test for definition (for crossing files)
+    def test_type_definition_for_class_constant
+      init("type_definition")
+
+      notify(
+        "textDocument/didOpen",
+        textDocument: { uri: @folder + "test.rb", version: 0, text: <<-END },
+class Foo
+end
+
+foo = Foo.new
+foo
+        END
+      )
+
+      expect_notification("typeprof.enableToggleButton") {|json| }
+      expect_request("workspace/codeLens/refresh") {|json| }
+
+      id = request(
+        "textDocument/typeDefinition",
+        textDocument: { uri: @folder + "test.rb" },
+        position: { line: 3, character: 6 },
+      )
+
+      expect_response(id) do |json|
+        assert_equal(2, json.size)
+
+        rbs_result = json.find { |r| r[:uri].end_with?(".rbs") }
+        rb_result = json.find { |r| r[:uri].end_with?(".rb") }
+
+        assert_not_nil(rbs_result, "RBS definition should be found")
+        assert_not_nil(rb_result, "Ruby definition should be found")
+
+        assert(rbs_result[:uri].end_with?("sig/test.rbs"))
+        assert(rb_result[:uri].end_with?("test.rb"))
+      end
+    end
+
+    def test_type_definition_for_local_variable
+      init("type_definition")
+
+      notify(
+        "textDocument/didOpen",
+        textDocument: { uri: @folder + "test.rb", version: 0, text: <<-END },
+class Foo
+end
+
+foo = Foo.new
+foo
+        END
+      )
+
+      expect_notification("typeprof.enableToggleButton") {|json| }
+      expect_request("workspace/codeLens/refresh") {|json| }
+
+      id = request(
+        "textDocument/typeDefinition",
+        textDocument: { uri: @folder + "test.rb" },
+        position: { line: 4, character: 0 },
+      )
+
+      expect_response(id) do |json|
+        assert_equal(2, json.size)
+
+        rbs_result = json.find { |r| r[:uri].end_with?(".rbs") }
+        rb_result = json.find { |r| r[:uri].end_with?(".rb") }
+
+        assert_not_nil(rbs_result, "RBS definition should be found")
+        assert_not_nil(rb_result, "Ruby definition should be found")
+
+        assert(rbs_result[:uri].end_with?("sig/test.rbs"))
+        assert(rb_result[:uri].end_with?("test.rb"))
+      end
+    end
   end
 end