diff --git a/pisi/db/componentdb.py b/pisi/db/componentdb.py
index 781a5fd7..2f647f51 100644
--- a/pisi/db/componentdb.py
+++ b/pisi/db/componentdb.py
@@ -194,7 +194,7 @@ componentdb = None
 
 def init():
     global componentdb
-    if componentdb:
+    if componentdb is not None:
         return componentdb
 
     componentdb = ComponentDB()
@@ -202,6 +202,6 @@ def init():
 
 def finalize():
     global componentdb
-    if componentdb:
+    if componentdb is not None:
         componentdb.close()
         componentdb = None
diff --git a/pisi/db/filesdb.py b/pisi/db/filesdb.py
index b9ac0bf7..6d21fa7e 100644
--- a/pisi/db/filesdb.py
+++ b/pisi/db/filesdb.py
@@ -76,7 +76,7 @@ filesdb = None
 
 def init():
     global filesdb
-    if filesdb:
+    if filesdb is not None:
         return filesdb
 
     filesdb = FilesDB()
@@ -84,6 +84,6 @@ def init():
 
 def finalize():
     global filesdb
-    if filesdb:
+    if filesdb is not None:
         filesdb.close()
         filesdb = None
diff --git a/pisi/db/installdb.py b/pisi/db/installdb.py
index 7551fb57..d55d3cb5 100644
--- a/pisi/db/installdb.py
+++ b/pisi/db/installdb.py
@@ -197,7 +197,7 @@ db = None
 
 def init():
     global db
-    if db:
+    if db is not None:
         return db
 
     db = InstallDB()
@@ -205,6 +205,6 @@ def init():
 
 def finalize():
     global db
-    if db:
+    if db is not None:
         db.close()
         db = None
diff --git a/pisi/db/packagedb.py b/pisi/db/packagedb.py
index 9086a445..135975d9 100644
--- a/pisi/db/packagedb.py
+++ b/pisi/db/packagedb.py
@@ -183,11 +183,16 @@ pkgdb = None
 
 def init():
     global pkgdb
+
+    if pkgdb is not None:
+        return pkgdb
+
     pkgdb = PackageDB()
     return pkgdb
 
 def finalize():
     global pkgdb
-    if pkgdb:
+
+    if pkgdb is not None:
         pkgdb.close()
         pkgdb = None
diff --git a/pisi/db/repodb.py b/pisi/db/repodb.py
index 17d23456..2274e49c 100644
--- a/pisi/db/repodb.py
+++ b/pisi/db/repodb.py
@@ -110,7 +110,7 @@ db = None
 def init():
     global db
 
-    if db:
+    if db is not None:
         return db
 
     db = RepoDB()
@@ -119,6 +119,6 @@ def init():
 def finalize():
     global db
 
-    if db:
+    if db is not None:
         db.close()
         db = None
diff --git a/pisi/db/sourcedb.py b/pisi/db/sourcedb.py
index e85931b2..4d67ed91 100644
--- a/pisi/db/sourcedb.py
+++ b/pisi/db/sourcedb.py
@@ -93,7 +93,7 @@ srcdb = None
 
 def init():
     global srcdb
-    if srcdb:
+    if srcdb is not None:
         return srcdb
 
     srcdb = SourceDB()
@@ -101,6 +101,6 @@ def init():
 
 def finalize():
     global srcdb
-    if srcdb:
+    if srcdb is not None:
         srcdb.close()
         srcdb = None