diff --git a/tests/scripts/test_psa_compliance.py b/tests/scripts/test_psa_compliance.py
index 5df479d..4008a5c 100755
--- a/tests/scripts/test_psa_compliance.py
+++ b/tests/scripts/test_psa_compliance.py
@@ -77,7 +77,7 @@
         subprocess.check_call([
             'cmake', '.',
                      '-GUnix Makefiles',
-                     '-B', library_build_dir
+                     '-B' + library_build_dir
         ])
         subprocess.check_call(['cmake', '--build', library_build_dir,
                                '-t', crypto_name])