diff --git a/.kokoro/requirements.in b/.kokoro/requirements.in
index cdc2d4ef..a4020358 100644
--- a/.kokoro/requirements.in
+++ b/.kokoro/requirements.in
@@ -7,3 +7,4 @@ wheel
 setuptools
 nox
 nh3
+proto-plus
diff --git a/.kokoro/requirements.txt b/.kokoro/requirements.txt
index b7c7c9b0..59a77546 100644
--- a/.kokoro/requirements.txt
+++ b/.kokoro/requirements.txt
@@ -446,7 +446,9 @@ nh3==0.2.18 \
     --hash=sha256:c8b3a1cebcba9b3669ed1a84cc65bf005728d2f0bc1ed2a6594a992e817f3a50 \
     --hash=sha256:de3ceed6e661954871d6cd78b410213bdcb136f79aafe22aa7182e028b8c7307 \
     --hash=sha256:f0eca9ca8628dbb4e916ae2491d72957fdd35f7a5d326b7032a345f111ac07fe
-    # via -r requirements.in
+    # via
+    #   -r requirements.in
+    #   readme-renderer
 nox==2022.11.21 \
     --hash=sha256:0e41a990e290e274cb205a976c4c97ee3c5234441a8132c8c3fd9ea3c22149eb \
     --hash=sha256:e21c31de0711d1274ca585a2c5fde36b1aa962005ba8e9322bf5eeed16dcd684
@@ -465,6 +467,10 @@ platformdirs==2.6.2 \
     --hash=sha256:83c8f6d04389165de7c9b6f0c682439697887bca0aa2f1c87ef1826be3584490 \
     --hash=sha256:e1fea1fe471b9ff8332e229df3cb7de4f53eeea4998d3b6bfff542115e998bd2
     # via virtualenv
+proto-plus==1.25.0 \
+    --hash=sha256:c91fc4a65074ade8e458e95ef8bac34d4008daa7cce4a12d6707066fca648961 \
+    --hash=sha256:fbb17f57f7bd05a68b7707e745e26528b0b3c34e378db91eef93912c54982d91
+    # via -r requirements.in
 protobuf==3.20.3 \
     --hash=sha256:03038ac1cfbc41aa21f6afcbcd357281d7521b4157926f30ebecc8d4ea59dcb7 \
     --hash=sha256:28545383d61f55b57cf4df63eebd9827754fd2dc25f80c5253f9184235db242c \