diff --git a/rpmUtils/transaction.py b/rpmUtils/transaction.py

index 778ed2db..96e0ffc3 100644

--- a/rpmUtils/transaction.py

+++ b/rpmUtils/transaction.py

@@ -119,11 +119,13 @@ class TransactionWrapper:

         tserrors = self.ts.run(cb.callback, '')

         self.ts.setFlags(origflags)

+        if tserrors is None:

+            return []

+        if not tserrors:

+            return ['Unknown error during transaction test in RPM']

         reserrors = []

-        if tserrors:

-            for (descr, (etype, mount, need)) in tserrors:

-                reserrors.append(descr)

-        

+        for (descr, (etype, mount, need)) in tserrors:

+            reserrors.append(descr)

         return reserrors