diff --git a/CHANGELOG.md b/CHANGELOG.md
index 73b95f9..7a8f9fe 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,20 +1,32 @@
 # Changelog
 
-### [1.2.3](https://github.com/googleapis/python-source-context/compare/v1.2.2...v1.2.3) (2022-05-05)
+## [1.2.4](https://github.com/googleapis/python-source-context/compare/v1.2.3...v1.2.4) (2022-06-03)
+
+
+### Bug Fixes
+
+* **deps:** require protobuf <4.0.0dev ([#87](https://github.com/googleapis/python-source-context/issues/87)) ([5b86140](https://github.com/googleapis/python-source-context/commit/5b86140b3a4ffa4c591722e127e4bbff64eab91e))
+
+
+### Documentation
+
+* fix changelog header to consistent size ([#88](https://github.com/googleapis/python-source-context/issues/88)) ([7b7fe62](https://github.com/googleapis/python-source-context/commit/7b7fe6278cf454196e89c18db63a20acd2c8aa23))
+
+## [1.2.3](https://github.com/googleapis/python-source-context/compare/v1.2.2...v1.2.3) (2022-05-05)
 
 
 ### Documentation
 
 * fix docstring for map fields ([614c640](https://github.com/googleapis/python-source-context/commit/614c640a224c6fcf0c1fd4656d871b3799508314))
 
-### [1.2.2](https://github.com/googleapis/python-source-context/compare/v1.2.1...v1.2.2) (2022-03-05)
+## [1.2.2](https://github.com/googleapis/python-source-context/compare/v1.2.1...v1.2.2) (2022-03-05)
 
 
 ### Bug Fixes
 
 * **deps:** require google-api-core>=1.31.5, >=2.3.2 ([#66](https://github.com/googleapis/python-source-context/issues/66)) ([0b06641](https://github.com/googleapis/python-source-context/commit/0b06641e0a648bdebf1539eaf12f666845795b80))
 
-### [1.2.1](https://www.github.com/googleapis/python-source-context/compare/v1.2.0...v1.2.1) (2021-11-01)
+## [1.2.1](https://www.github.com/googleapis/python-source-context/compare/v1.2.0...v1.2.1) (2021-11-01)
 
 
 ### Bug Fixes
@@ -48,21 +60,21 @@
 
 * bump release level to production/stable ([#31](https://www.github.com/googleapis/python-source-context/issues/31)) ([139188c](https://www.github.com/googleapis/python-source-context/commit/139188cb7a7850878b91756bacb0daf758cdcf2a))
 
-### [0.1.4](https://www.github.com/googleapis/python-source-context/compare/v0.1.3...v0.1.4) (2021-09-24)
+## [0.1.4](https://www.github.com/googleapis/python-source-context/compare/v0.1.3...v0.1.4) (2021-09-24)
 
 
 ### Bug Fixes
 
 * add 'dict' annotation type to 'request' ([0039f92](https://www.github.com/googleapis/python-source-context/commit/0039f92abf768992bdd79e68fb99407cd0e47629))
 
-### [0.1.3](https://www.github.com/googleapis/python-source-context/compare/v0.1.2...v0.1.3) (2021-08-23)
+## [0.1.3](https://www.github.com/googleapis/python-source-context/compare/v0.1.2...v0.1.3) (2021-08-23)
 
 
 ### Documentation
 
 * Migrate default branch to main ([#17](https://www.github.com/googleapis/python-source-context/issues/17)) ([6011f91](https://www.github.com/googleapis/python-source-context/commit/6011f91031abce8a71c5b6891a1ee8e241d580e0))
 
-### [0.1.2](https://www.github.com/googleapis/python-source-context/compare/v0.1.1...v0.1.2) (2021-07-29)
+## [0.1.2](https://www.github.com/googleapis/python-source-context/compare/v0.1.1...v0.1.2) (2021-07-29)
 
 
 ### Documentation
@@ -74,7 +86,7 @@
 
 * release as 0.1.2 ([#11](https://www.github.com/googleapis/python-source-context/issues/11)) ([1581f56](https://www.github.com/googleapis/python-source-context/commit/1581f56aae3879407e6b2d6de2012760f976deaf))
 
-### [0.1.1](https://www.github.com/googleapis/python-source-context/compare/v0.1.0...v0.1.1) (2021-07-21)
+## [0.1.1](https://www.github.com/googleapis/python-source-context/compare/v0.1.0...v0.1.1) (2021-07-21)
 
 
 ### Bug Fixes
diff --git a/setup.py b/setup.py
index ee26467..4cb86da 100644
--- a/setup.py
+++ b/setup.py
@@ -21,7 +21,7 @@
 
 name = "google-cloud-source-context"
 description = "Python client for Source Context"
-version = "1.2.3"
+version = "1.2.4"
 release_status = "Development Status :: 5 - Production/Stable"
 url = "https://github.com/googleapis/python-source-context"
 dependencies = [
@@ -29,7 +29,8 @@
     # Until this issue is closed
     # https://github.com/googleapis/google-cloud-python/issues/10566
     "google-api-core[grpc] >= 1.31.5, <3.0.0dev,!=2.0.*,!=2.1.*,!=2.2.*,!=2.3.0",
-    "proto-plus >= 1.15.0",
+    "proto-plus >= 1.15.0, <2.0.0dev",
+    "protobuf >= 3.19.0, <4.0.0dev",
 ]
 
 package_root = os.path.abspath(os.path.dirname(__file__))
diff --git a/testing/constraints-3.6.txt b/testing/constraints-3.6.txt
index be5a64f..786e637 100644
--- a/testing/constraints-3.6.txt
+++ b/testing/constraints-3.6.txt
@@ -6,3 +6,4 @@
 # Then this file should have google-cloud-foo==1.14.0
 google-api-core==1.31.5
 proto-plus==1.15.0
+protobuf==3.19.0
diff --git a/testing/constraints-3.7.txt b/testing/constraints-3.7.txt
index e69de29..786e637 100644
--- a/testing/constraints-3.7.txt
+++ b/testing/constraints-3.7.txt
@@ -0,0 +1,9 @@
+# This constraints file is used to check that lower bounds
+# are correct in setup.py
+# List all library dependencies and extras in this file.
+# Pin the version to the lower bound.
+# e.g., if setup.py has "google-cloud-foo >= 1.14.0, < 2.0.0dev",
+# Then this file should have google-cloud-foo==1.14.0
+google-api-core==1.31.5
+proto-plus==1.15.0
+protobuf==3.19.0