diff --git a/stdnum/util.py b/stdnum/util.py
index 11b58dd7..6c9571d1 100644
--- a/stdnum/util.py
+++ b/stdnum/util.py
@@ -237,7 +237,7 @@ def get_cc_module(cc, name):
         mod = __import__('stdnum.%s' % cc, globals(), locals(), [str(name)])
         return getattr(mod, name, None)
     except ImportError:
-        return
+        return None
 
 
 # this is a cache of SOAP clients
diff --git a/stdnum/vatin.py b/stdnum/vatin.py
index a8553d2c..5a5bdb58 100644
--- a/stdnum/vatin.py
+++ b/stdnum/vatin.py
@@ -44,7 +44,7 @@
 >>> validate('XX')
 Traceback (most recent call last):
     ...
-InvalidComponent: ...
+ImportError: ...
 """
 
 import re
@@ -53,6 +53,10 @@
 from stdnum.util import clean, get_cc_module
 
 
+# regular expression for matching country codes.
+_country_code_re = re.compile(r'^[a-z]{2}$')
+
+
 # Cache of country code modules
 _country_modules = dict()
 
@@ -61,12 +65,12 @@ def _get_cc_module(cc):
     """Get the VAT number module based on the country code."""
     # Greece uses a "wrong" country code, special case for Northern Ireland
     cc = cc.lower().replace('el', 'gr').replace('xi', 'gb')
-    if not re.match(r'^[a-z]{2}$', cc):
-        raise InvalidFormat()
+    if not _country_code_re.match(cc):
+        raise ImportError()
     if cc not in _country_modules:
         _country_modules[cc] = get_cc_module(cc, 'vat')
     if not _country_modules[cc]:
-        raise InvalidComponent()  # unknown/unsupported country code
+        raise ImportError()
     return _country_modules[cc]
 
 
@@ -94,5 +98,7 @@ def is_valid(number):
     """Check if the number is a valid VAT number."""
     try:
         return bool(validate(number))
+    except ImportError:
+        return False
     except ValidationError:
         return False
diff --git a/tests/test_vatin.doctest b/tests/test_vatin.doctest
index 4d785c31..f0d9e0ba 100644
--- a/tests/test_vatin.doctest
+++ b/tests/test_vatin.doctest
@@ -61,11 +61,11 @@ Try validating not specifying a country:
 >>> vatin.validate('')
 Traceback (most recent call last):
     ...
-InvalidFormat: ...
+ImportError: ...
 >>> vatin.validate('00')
 Traceback (most recent call last):
     ...
-InvalidFormat: ...
+ImportError: ...
 
 
 Try to validate for countries with no VAT validation:
@@ -73,8 +73,26 @@ Try to validate for countries with no VAT validation:
 >>> vatin.validate('XX')
 Traceback (most recent call last):
     ...
-InvalidComponent: ...
+ImportError: ...
 >>> vatin.validate('US')
 Traceback (most recent call last):
     ...
-InvalidComponent: ...
+ImportError: ...
+
+
+Check is_valid for several scenarios:
+
+>>> vatin.is_valid('FR 40 303 265 045')
+True
+>>> vatin.is_valid('FR 40 303')
+False
+>>> vatin.is_valid('FR')
+False
+>>> vatin.is_valid('')
+False
+>>> vatin.is_valid('00')
+False
+>>> vatin.is_valid('XX')
+False
+>>> vatin.is_valid('US')
+False