diff --git a/env/cpu/py3-master.yml b/env/cpu/py3-master.yml
index fe23fc87de..b85562d552 100644
--- a/env/cpu/py3-master.yml
+++ b/env/cpu/py3-master.yml
@@ -4,6 +4,8 @@ dependencies:
   - python=3.5
   - pip
   - perl
+  # In the -master pipeline, we test without numba. Numba is an optional
+  # dependency and GluonNLP needs to work both with and without numba installed.
   - pip:
     - numpy==1.17.4
     - cython
diff --git a/env/cpu/py3.yml b/env/cpu/py3.yml
index 0506fdfa00..87c40c63c2 100644
--- a/env/cpu/py3.yml
+++ b/env/cpu/py3.yml
@@ -16,7 +16,7 @@ dependencies:
     - nbsphinx>=0.3.4,<0.4
     - ipython
     - ipykernel
-    - numba==0.46
+    - numba==0.47
     - https://github.com/szha/mx-theme/tarball/master
     - seaborn
     - jieba
diff --git a/env/docker/py3.yml b/env/docker/py3.yml
index 44c9e82b37..12db5c5fe8 100644
--- a/env/docker/py3.yml
+++ b/env/docker/py3.yml
@@ -16,7 +16,7 @@ dependencies:
     - nbsphinx>=0.3.4,<0.4
     - ipython
     - ipykernel
-    - numba==0.46
+    - numba==0.47
     - https://github.com/szha/mx-theme/tarball/master
     - seaborn
     - jieba
diff --git a/env/gpu/py3-master.yml b/env/gpu/py3-master.yml
index 2c61506aea..58067570d9 100644
--- a/env/gpu/py3-master.yml
+++ b/env/gpu/py3-master.yml
@@ -7,6 +7,8 @@ dependencies:
   - pandoc=1.19.2
   - tornado=5.1.1
   - sphinx=2.2.1
+  # In the -master pipeline, we test without numba. Numba is an optional
+  # dependency and GluonNLP needs to work both with and without numba installed.
   - pip:
     - numpy==1.17.4
     - notedown==1.5.1
@@ -16,7 +18,6 @@ dependencies:
     - nbsphinx>=0.3.4,<0.4
     - ipython
     - ipykernel
-    - numba==0.46
     - https://github.com/szha/mx-theme/tarball/master
     - seaborn
     - jieba
diff --git a/env/gpu/py3.yml b/env/gpu/py3.yml
index 0506fdfa00..87c40c63c2 100644
--- a/env/gpu/py3.yml
+++ b/env/gpu/py3.yml
@@ -16,7 +16,7 @@ dependencies:
     - nbsphinx>=0.3.4,<0.4
     - ipython
     - ipykernel
-    - numba==0.46
+    - numba==0.47
     - https://github.com/szha/mx-theme/tarball/master
     - seaborn
     - jieba