diff --git a/bubbles/backends/mongo/objects.py b/bubbles/backends/mongo/objects.py
index e981e04..8a3acdd 100644
--- a/bubbles/backends/mongo/objects.py
+++ b/bubbles/backends/mongo/objects.py
@@ -36,6 +36,7 @@ def default_store(database, host, port):
 
 class MongoDBStore(DataStore):
     __identifier__ = "mongo"
+    __extension_name__ = "mongo"
 
     def __init__(self, database, host='localhost', port=27017, client=None):
         """Creates a MongoDB data object store."""
@@ -58,7 +59,7 @@ def objects(self, names=None):
         raise NotImplementedError
 
     def create(self, name, fields, replace=False):
-        obj = MongoDBCollection(name, fields=fields, store=self)
+        obj = MongoDBCollection(name, fields=fields, store=self, truncate=replace)
 
         if replace:
             # The only way how to check for collection existence is to look if
@@ -81,7 +82,7 @@ class MongoDBCollection(DataObject):
 
     def __init__(self, collection, fields, truncate=False,
                  expand=False,
-                 database=None, host='localhsot', port=27017,
+                 database=None, host='localhost', port=27017,
                  store=None):
         """Creates a MongoDB data object.
 
diff --git a/bubbles/backends/sql/ops.py b/bubbles/backends/sql/ops.py
index 9a38267..7ff1dcf 100644
--- a/bubbles/backends/sql/ops.py
+++ b/bubbles/backends/sql/ops.py
@@ -82,7 +82,7 @@ def _(ctx, src, key, value, discard=False):
 
 
 @filter_by_range.register("sql")
-def _(ctx, src, field, low, high, discard=False):
+def _(ctx, src, key, low, high, discard=False):
     """Filter by range: field should be between low and high."""
 
     statement = src.sql_statement()
diff --git a/bubbles/extensions.py b/bubbles/extensions.py
index 15ce3c8..8976522 100644
--- a/bubbles/extensions.py
+++ b/bubbles/extensions.py
@@ -20,7 +20,7 @@
 _default_modules = {
     "store": {
         "sql":"bubbles.backends.sql.objects",
-        "mongo":"bubbles.backends.sql.mongo",
+        "mongo":"bubbles.backends.mongo.objects",
         "csv":"bubbles.backends.text.objects",
         "datapackage":"bubbles.datapackage",
         "datapackages":"bubbles.datapackage",
diff --git a/bubbles/operation.py b/bubbles/operation.py
index e41ec21..5ba1891 100644
--- a/bubbles/operation.py
+++ b/bubbles/operation.py
@@ -238,7 +238,7 @@ def resolution_order(self, representations):
         return matches
 
 
-    def register(self, *signature, name=None):
+    def register(self, *signatures, name=None):
         sig = None
 
         def register_function(func):
@@ -256,8 +256,8 @@ def register_function(func):
             func.__name__ = self.name
             return func
 
-        if signature and callable(signature[0]):
-            func, *signature = signature
+        if signatures and callable(signatures[0]):
+            func, *signature = signatures
 
             # Create default signature if none is provided
             if not signature:
@@ -266,7 +266,7 @@ def register_function(func):
             sig = Signature(*signature)
             return register_function(func)
         else:
-            sig = Signature(*signature)
+            sig = Signature(*signatures)
             return register_function
 
     def __str__(self):
@@ -307,4 +307,3 @@ def decorator(func):
         return decorator
 
 
-
diff --git a/examples/hello_mongo.py b/examples/hello_mongo.py
new file mode 100644
index 0000000..1a3d322
--- /dev/null
+++ b/examples/hello_mongo.py
@@ -0,0 +1,25 @@
+import bubbles
+
+# Follow the comments – there is a line to be uncommented
+
+URL = "https://raw.github.com/Stiivi/cubes/master/examples/hello_world/data.csv"
+
+# Prepare list of stores, we just need one temporary SQL store
+
+stores = {
+    "target": bubbles.open_store("mongo", database="sample", host='127.0.0.1', port=27017)
+}
+
+
+p = bubbles.Pipeline(stores=stores)
+p.source_object("csv_source", resource=URL, encoding="utf8")
+p.retype({"Amount (US$, Millions)": "integer"})
+
+# We create a table
+# Uncomment this line and see the difference in debug messages
+p.create("target", "data")
+
+p.aggregate("Category", "Amount (US$, Millions)")
+p.pretty_print()
+p.run()
+