diff --git a/installsystems/database.py b/installsystems/database.py
index c723e26eb352597028c5d7653b1527d7265ba93c..f9dc86ee7cdabd61c95ce9bae4cc9bea6ff862de 100644
--- a/installsystems/database.py
+++ b/installsystems/database.py
@@ -52,11 +52,11 @@ class Database(object):
             r = self.ask("SELECT value FROM misc WHERE key = 'version'").fetchone()
             if r is None:
                 raise TypeError()
-            self.version = r[0]
+            self.version = float(r[0])
         except:
-            self.version = u"1"
+            self.version = 1.0
         # we only support database v1
-        if self.version != u"1":
+        if self.version >= 2.0:
             debug("Invalid database format: %s" % self.version)
             raise Exception("Invalid database format")
         # we make a query to be sure format is valid
diff --git a/installsystems/image.py b/installsystems/image.py
index 87a266f397e3c56c697b0894b7eec6b8a093f9de..9843f612c81c6a4cf4128ff0513f1d5ad0783433 100644
--- a/installsystems/image.py
+++ b/installsystems/image.py
@@ -10,6 +10,7 @@ import os
 import stat
 import time
 import json
+import math
 import difflib
 import ConfigParser
 import subprocess
@@ -32,6 +33,8 @@ class Image(object):
     Abstract class of images
     '''
 
+    # format should be a float  X.Y but for compatibility reason it's a string
+    # before version 6, it's strict string comparaison
     format = "1"
     extension = ".isimage"
 
@@ -546,8 +549,17 @@ class PackageImage(Image):
         desc = {}
         # check format
         img_format = self._tarball.get_str("format")
-        if img_format != self.format:
-            raise Exception("Invalid tarball image format")
+        try:
+            print img_format
+            print self.format
+            print math.floor(float(self.format)) + 1.0
+            #print(int(self.format) + 1)
+            print 'toto'
+            if float(img_format) >= math.floor(float(self.format)) + 1.0:
+                print 'otot'
+                raise Exception()
+        except:
+            raise Exception("Invalid image format %s" % img_format)
         desc["format"] = img_format
         # check description
         try: