diff --git a/setup.py b/setup.py
index 3070985f1..34c92ad2b 100755
--- a/setup.py
+++ b/setup.py
@@ -244,6 +244,8 @@ def setup_package():
                 "cuda91": ["cupy-cuda91>=4.0"],
                 "cuda92": ["cupy-cuda92>=4.0"],
                 "cuda100": ["cupy-cuda100>=4.0"],
+                # Language tokenizers with external dependencies
+                "ja": ["mecab-python3==0.7"],
             },
             python_requires=">=2.7,!=3.0.*,!=3.1.*,!=3.2.*,!=3.3.*",
             classifiers=[