diff --git a/benchmark/bin/pyproto_cpp-carsales b/benchmark/bin/pyproto_cpp-carsales
index 2c068fb..c9a2788 100755
--- a/benchmark/bin/pyproto_cpp-carsales
+++ b/benchmark/bin/pyproto_cpp-carsales
@@ -1,4 +1,4 @@
 #!/usr/bin/env bash
 
-PROTOCOL_BUFFERS_PYTHON_IMPLEMENTATION=cpp
+export PROTOCOL_BUFFERS_PYTHON_IMPLEMENTATION=cpp
 pyproto-carsales $@
diff --git a/benchmark/bin/pyproto_cpp-catrank b/benchmark/bin/pyproto_cpp-catrank
index eedf594..5297843 100755
--- a/benchmark/bin/pyproto_cpp-catrank
+++ b/benchmark/bin/pyproto_cpp-catrank
@@ -1,4 +1,4 @@
 #!/usr/bin/env bash
 
-PROTOCOL_BUFFERS_PYTHON_IMPLEMENTATION=cpp
+export PROTOCOL_BUFFERS_PYTHON_IMPLEMENTATION=cpp
 pyproto-catrank $@
diff --git a/benchmark/bin/pyproto_cpp-eval b/benchmark/bin/pyproto_cpp-eval
index 5a81d9b..88361fc 100755
--- a/benchmark/bin/pyproto_cpp-eval
+++ b/benchmark/bin/pyproto_cpp-eval
@@ -1,4 +1,4 @@
 #!/usr/bin/env bash
 
-PROTOCOL_BUFFERS_PYTHON_IMPLEMENTATION=cpp
+export PROTOCOL_BUFFERS_PYTHON_IMPLEMENTATION=cpp
 pyproto-eval $@