diff --git a/kuksa-client/pyproject.toml b/kuksa-client/pyproject.toml
index 46cb1b0..d6358d7 100644
--- a/kuksa-client/pyproject.toml
+++ b/kuksa-client/pyproject.toml
@@ -2,6 +2,8 @@
 requires = [
     # Make sure to use the same exact version criteria in setup.cfg and update requirements.txt after changing
     "grpcio-tools==1.68.0",
+    # Explicit protobuf pin matching setup.cfg to avoid gencode/runtime version mismatch. Fixes #54.
+    "protobuf>=5.29.6,<6.0dev",
     "setuptools>=42",
     "setuptools-git-versioning",
     "wheel",
diff --git a/kuksa-client/setup.cfg b/kuksa-client/setup.cfg
index 1bf3e85..3bceb00 100644
--- a/kuksa-client/setup.cfg
+++ b/kuksa-client/setup.cfg
@@ -29,6 +29,11 @@ install_requires =
     pygments >= 2.15
     # Make sure to use the same version criteria in pyproject.toml and update requirements.txt after changing
     grpcio-tools == 1.68.0
+    # Explicit protobuf pin: grpcio-tools 1.68.0 resolves to protobuf 5.29.x; the
+    # generated _pb2 files must be loaded by a compatible runtime version.
+    # Without this constraint, pip may install a mismatched version and raise
+    # "Detected incompatible Protobuf Gencode/Runtime versions". Fixes #54.
+    protobuf >= 5.29.6, < 6.0dev
     jsonpath-ng >= 1.5.3
 packages = find: