diff --git a/AUTHORS b/AUTHORS
index 7a787ec74f..4a027fdd6e 100644
--- a/AUTHORS
+++ b/AUTHORS
@@ -112,6 +112,7 @@ answer newbie questions, and generally made Django that much better:
     Garth Kidd <http://www.deadlybloodyserious.com/>
     kilian <kilian.cavalotti@lip6.fr>
     Sune Kirkeby <http://ibofobi.dk/>
+    Bastian Kleineidam <calvin@debian.org>
     Cameron Knight (ckknight)
     Meir Kriheli <http://mksoft.co.il/>
     Bruce Kroeze <http://coderseye.com/>
diff --git a/django/db/backends/ado_mssql/base.py b/django/db/backends/ado_mssql/base.py
index 9eaa5625d9..8dcb98ce61 100644
--- a/django/db/backends/ado_mssql/base.py
+++ b/django/db/backends/ado_mssql/base.py
@@ -76,10 +76,11 @@ class DatabaseWrapper(local):
         return cursor
 
     def _commit(self):
-        return self.connection.commit()
+        if self.connection is not None:
+            return self.connection.commit()
 
     def _rollback(self):
-        if self.connection:
+        if self.connection is not None:
             return self.connection.rollback()
 
     def close(self):
diff --git a/django/db/backends/mysql/base.py b/django/db/backends/mysql/base.py
index 4ccb1fe564..4bd87518e8 100644
--- a/django/db/backends/mysql/base.py
+++ b/django/db/backends/mysql/base.py
@@ -108,10 +108,11 @@ class DatabaseWrapper(local):
         return cursor
 
     def _commit(self):
-        self.connection.commit()
+        if self.connection is not None:
+            self.connection.commit()
 
     def _rollback(self):
-        if self.connection:
+        if self.connection is not None:
             try:
                 self.connection.rollback()
             except Database.NotSupportedError:
diff --git a/django/db/backends/oracle/base.py b/django/db/backends/oracle/base.py
index 229e203ca1..d52ae33c2e 100644
--- a/django/db/backends/oracle/base.py
+++ b/django/db/backends/oracle/base.py
@@ -43,10 +43,11 @@ class DatabaseWrapper(local):
         return FormatStylePlaceholderCursor(self.connection)
 
     def _commit(self):
-        self.connection.commit()
+        if self.connection is not None:
+            self.connection.commit()
 
     def _rollback(self):
-        if self.connection:
+        if self.connection is not None:
             try:
                 self.connection.rollback()
             except Database.NotSupportedError:
diff --git a/django/db/backends/postgresql/base.py b/django/db/backends/postgresql/base.py
index 89695b0c4b..54be422ae2 100644
--- a/django/db/backends/postgresql/base.py
+++ b/django/db/backends/postgresql/base.py
@@ -92,10 +92,11 @@ class DatabaseWrapper(local):
         return cursor
 
     def _commit(self):
-        return self.connection.commit()
+        if self.connection is not None:
+            return self.connection.commit()
 
     def _rollback(self):
-        if self.connection:
+        if self.connection is not None:
             return self.connection.rollback()
 
     def close(self):
diff --git a/django/db/backends/postgresql_psycopg2/base.py b/django/db/backends/postgresql_psycopg2/base.py
index 9b319ad3c7..e4724e46fb 100644
--- a/django/db/backends/postgresql_psycopg2/base.py
+++ b/django/db/backends/postgresql_psycopg2/base.py
@@ -60,10 +60,11 @@ class DatabaseWrapper(local):
         return cursor
 
     def _commit(self):
-        return self.connection.commit()
+        if self.connection is not None:
+            return self.connection.commit()
 
     def _rollback(self):
-        if self.connection:
+        if self.connection is not None:
             return self.connection.rollback()
 
     def close(self):
diff --git a/django/db/backends/sqlite3/base.py b/django/db/backends/sqlite3/base.py
index ce343e189e..4b8a1c64a8 100644
--- a/django/db/backends/sqlite3/base.py
+++ b/django/db/backends/sqlite3/base.py
@@ -67,10 +67,11 @@ class DatabaseWrapper(local):
             return cursor
 
     def _commit(self):
-        self.connection.commit()
+        if self.connection is not None:
+            self.connection.commit()
 
     def _rollback(self):
-        if self.connection:
+        if self.connection is not None:
             self.connection.rollback()
 
     def close(self):