diff --git a/tools/ostestr_compat_shim.sh b/tools/ostestr_compat_shim.sh
new file mode 100755
index 00000000..195cbd24
--- /dev/null
+++ b/tools/ostestr_compat_shim.sh
@@ -0,0 +1,8 @@
+#!/bin/sh
+
+# preserve old behavior of using an arg as a regex when '--' is not present
+case $@ in
+    (*--*) ostestr $@;;
+    ('') ostestr;;
+    (*) ostestr --regex "$@"
+esac
diff --git a/tox.ini b/tox.ini
index 0ccb1244..aa69473e 100644
--- a/tox.ini
+++ b/tox.ini
@@ -17,7 +17,7 @@ deps = -r{toxinidir}/requirements.txt
 whitelist_externals = sh
                       find
 commands = find . -type f -name "*.py[c|o]" -delete
-           ostestr '{posargs}'
+           {toxinidir}/tools/ostestr_compat_shim.sh {posargs}
 
 [testenv:fullstack]
 basepython = python2.7