diff --git a/setup.py b/setup.py
index 202b94a77..b5797157b 100755
--- a/setup.py
+++ b/setup.py
@@ -68,6 +68,7 @@ class PrebuildCommand(Command):
         try:
             proto_srcs = glob.glob(os.path.join(TREZOR_COMMON, "protob", "*.proto"))
             subprocess.check_call([
+                sys.executable,
                 os.path.join(TREZOR_COMMON, "protob", "pb2py"),
                 "-o", os.path.join(CWD, "trezorlib", "messages"),
                 "-P", "..protobuf",