diff --git a/lib/spack/spack/cmd/bootstrap.py b/lib/spack/spack/cmd/bootstrap.py
index 60e2bd3a1141b11f849afa0c5cb2d0d79a48c610..a79ef4aa68039b9080242cbcaa2a09d1b396a1c7 100644
--- a/lib/spack/spack/cmd/bootstrap.py
+++ b/lib/spack/spack/cmd/bootstrap.py
@@ -28,7 +28,7 @@
 from llnl.util.filesystem import join_path, mkdirp
 
 import spack
-from spack.util.executable import which
+from spack.util.executable import ProcessError, which
 
 _SPACK_UPSTREAM = 'https://github.com/llnl/spack'