diff --git a/packages/google-cloud-python-speech/setup.py b/packages/google-cloud-python-speech/setup.py
index c38fc8351c50..1baa782691cd 100644
--- a/packages/google-cloud-python-speech/setup.py
+++ b/packages/google-cloud-python-speech/setup.py
@@ -31,7 +31,7 @@
 dependencies = [
     "google-api-core[grpc] >= 1.32.0, <3.0.0dev,!=2.0.*,!=2.1.*,!=2.2.*,!=2.3.*,!=2.4.*,!=2.5.*,!=2.6.*,!=2.7.*",
     "proto-plus >= 1.22.0, <2.0.0dev",
-    "protobuf >= 3.20.2, <5.0.0dev",
+    "protobuf>=3.19.5,<5.0.0dev,!=3.20.0,!=3.20.1,!=4.21.0,!=4.21.1,!=4.21.2,!=4.21.3,!=4.21.4,!=4.21.5",
 ]
 extras = {"libcst": "libcst >= 0.2.5"}
 
diff --git a/packages/google-cloud-python-speech/testing/constraints-3.7.txt b/packages/google-cloud-python-speech/testing/constraints-3.7.txt
index eb58105b1562..12b4d1428b2b 100644
--- a/packages/google-cloud-python-speech/testing/constraints-3.7.txt
+++ b/packages/google-cloud-python-speech/testing/constraints-3.7.txt
@@ -8,4 +8,4 @@
 google-api-core==1.32.0
 libcst==0.2.5
 proto-plus==1.22.0
-protobuf==3.20.2
+protobuf==3.19.5