diff --git a/etiquette/exceptions.py b/etiquette/exceptions.py
index 95e0ca8..78a3eb6 100644
--- a/etiquette/exceptions.py
+++ b/etiquette/exceptions.py
@@ -152,6 +152,12 @@ class WrongLogin(EtiquetteException):
 
 
 # GENERAL ERRORS
+class BadDataDirectory(EtiquetteException):
+    '''
+    Raised by PhotoDB __init__ if the requested data_directory is invalid.
+    '''
+    error_message = 'Bad data directory "{}"'
+
 OUTOFDATE = '''
 Database is out of date. {current} should be {new}.
 Please use utilities\\database_upgrader.py
diff --git a/etiquette/photodb.py b/etiquette/photodb.py
index 65f5791..7eb03df 100644
--- a/etiquette/photodb.py
+++ b/etiquette/photodb.py
@@ -1095,6 +1095,9 @@ class PhotoDB(
 
         data_directory = helpers.remove_path_badchars(data_directory, allowed=':/\\')
         self.data_directory = pathclass.Path(data_directory)
+
+        if self.data_directory.exists and not self.data_directory.is_dir:
+            raise exceptions.BadDataDirectory(self.data_directory.absolute_path)
         os.makedirs(self.data_directory.absolute_path, exist_ok=True)
 
         self.log = logging.getLogger('etiquette:%s' % self.data_directory.absolute_path)