diff --git a/.hgignore b/.hgignore
index 1b85cd9..913ee1b 100644
--- a/.hgignore
+++ b/.hgignore
@@ -1,3 +1,6 @@
 syntax: glob
 __pycache__/*
 locale/convert_de2en.py
+build/*
+mds_cashbook_media.egg-info/*
+dist/*
diff --git a/line.py b/line.py
index a7a482d..3949a8b 100644
--- a/line.py
+++ b/line.py
@@ -5,7 +5,7 @@
 
 import mimetypes, magic
 from io import BytesIO
-from PIL import Image
+from PIL import Image, UnidentifiedImageError
 from trytond.model import fields
 from trytond.pool import Pool, PoolMeta
 from trytond.config import config
@@ -65,7 +65,10 @@ class Line(metaclass=PoolMeta):
         """
         image_data2 = None
         with BytesIO(image_data) as fhdl:
-            image = Image.open(fhdl, 'r')
+            try :
+                image = Image.open(fhdl, 'r')
+            except UnidentifiedImageError:
+                raise UserError(gettext('cashbook_media.msg_file_unknown_type'))
 
             (width, height) = image.size
             if (width > image_limit) or (height > image_limit):
diff --git a/locale/de.po b/locale/de.po
index 69df498..052a9fb 100644
--- a/locale/de.po
+++ b/locale/de.po
@@ -14,6 +14,10 @@ msgctxt "model:ir.message,text:msg_file_invalid_mime"
 msgid "The file type '%(fmime)s' of the record '%(recname)s' is not allowed. (allowed: PNG, JPG, PDF)"
 msgstr "Der Dateityp '%(fmime)s' des Datensatzes '%(recname)s' ist nicht zugelassen. (erlaubt: PNG, JPG, PDF)"
 
+msgctxt "model:ir.message,text:msg_file_unknown_type"
+msgid "cannot identify image file"
+msgstr "Bilddatei kann nicht identifiziert werden"
+
 
 #################
 # cashbook.line #
diff --git a/locale/en.po b/locale/en.po
index 956e614..5ff9df6 100644
--- a/locale/en.po
+++ b/locale/en.po
@@ -10,6 +10,10 @@ msgctxt "model:ir.message,text:msg_file_invalid_mime"
 msgid "The file type '%(fmime)s' of the record '%(recname)s' is not allowed. (allowed: PNG, JPG, PDF)"
 msgstr "The file type '%(fmime)s' of the record '%(recname)s' is not allowed. (allowed: PNG, JPG, PDF)"
 
+msgctxt "model:ir.message,text:msg_file_unknown_type"
+msgid "cannot identify image file"
+msgstr "cannot identify image file"
+
 msgctxt "view:cashbook.line:"
 msgid "Image/PDF"
 msgstr "Image/PDF"
diff --git a/message.xml b/message.xml
index d88ff9a..3582d1e 100644
--- a/message.xml
+++ b/message.xml
@@ -11,6 +11,9 @@ full copyright notices and license terms. -->
         <record model="ir.message" id="msg_file_invalid_mime">
             <field name="text">The file type '%(fmime)s' of the record '%(recname)s' is not allowed. (allowed: PNG, JPG, PDF)</field>
         </record>
+        <record model="ir.message" id="msg_file_unknown_type">
+            <field name="text">cannot identify image file</field>
+        </record>
 
     </data>
 </tryton>