diff --git a/tools/mypywrap.sh b/tools/mypywrap.sh
old mode 100644
new mode 100755
index 0b4c51e6189..b1ada5f838c
--- a/tools/mypywrap.sh
+++ b/tools/mypywrap.sh
@@ -1,4 +1,4 @@
-#!/bin/sh
+#!/bin/bash
 #
 # A wrapper around mypy that allows us to specify what files to run 'mypy' type
 # checks on. Intended to be invoked via tox:
diff --git a/tox.ini b/tox.ini
index c4095812dac..ecc6fff75d5 100644
--- a/tox.ini
+++ b/tox.ini
@@ -172,7 +172,7 @@ description =
   Run type checks.
 envdir = {toxworkdir}/pep8
 commands =
-  bash tools/mypywrap.sh {posargs}
+  {toxinidir}/tools/mypywrap.sh {posargs}
 
 [flake8]
 # Following checks are ignored on purpose.