diff --git a/CHANGES b/CHANGES
index 5828de634..7b312a69a 100644
--- a/CHANGES
+++ b/CHANGES
@@ -7,6 +7,7 @@ Version 0.16
 ------------
 
 (bugfix release, released on X)
+- Fix typo preventing the security confirmation prompt from working (#303)
 - Improve handling of systems with improperly configured file system encoding (#289)
 - Fix "All archives" output for attic info. (#183)
 - More user friendly error message when repository key file is not found (#236)
diff --git a/attic/cache.py b/attic/cache.py
index 95017b61b..8a38d0f9a 100644
--- a/attic/cache.py
+++ b/attic/cache.py
@@ -68,7 +68,7 @@ class Cache(object):
         if env_var_override and os.environ.get(env_var_override):
             print("Yes (From {})".format(env_var_override))
             return True
-        if sys.stdin.isatty():
+        if not sys.stdin.isatty():
             return False
         try:
             answer = input('Do you want to continue? [yN] ')
diff --git a/attic/testsuite/archiver.py b/attic/testsuite/archiver.py
index c115b460f..372a1e052 100644
--- a/attic/testsuite/archiver.py
+++ b/attic/testsuite/archiver.py
@@ -106,18 +106,19 @@ class ArchiverTestCaseBase(AtticTestCase):
             self.assert_equal(exit_code, ret)
             return output
         args = list(args)
-        stdout, stderr = sys.stdout, sys.stderr
+        stdin, stdout, stderr = sys.stdin, sys.stdout, sys.stderr
         try:
+            sys.stdin = StringIO()
             output = StringIO()
             sys.stdout = sys.stderr = output
             ret = self.archiver.run(args)
-            sys.stdout, sys.stderr = stdout, stderr
+            sys.stdin, sys.stdout, sys.stderr = stdin, stdout, stderr
             if ret != exit_code:
                 print(output.getvalue())
             self.assert_equal(exit_code, ret)
             return output.getvalue()
         finally:
-            sys.stdout, sys.stderr = stdout, stderr
+            sys.stdin, sys.stdout, sys.stderr = stdin, stdout, stderr
 
     def create_src_archive(self, name):
         self.attic('create', self.repository_location + '::' + name, src_dir)