diff --git a/lib/spack/spack/cmd/module.py b/lib/spack/spack/cmd/module.py
index 916bb656466..0d980bc9182 100644
--- a/lib/spack/spack/cmd/module.py
+++ b/lib/spack/spack/cmd/module.py
@@ -65,7 +65,7 @@ def setup_parser(subparser):
         help='Generate shell script (instead of input for module command)')
 
     find_parser.add_argument(
-        '-p', '--prefix', dest='prefix',
+        '-p', '--prefix', dest='prefix', default='',
         help='Prepend to module names when issuing module load commands')
     _add_common_arguments(find_parser)