diff --git a/stix2/utils.py b/stix2/utils.py
index f2bac52..da04a3e 100644
--- a/stix2/utils.py
+++ b/stix2/utils.py
@@ -27,8 +27,8 @@ NOW = object()
 STIX_UNMOD_PROPERTIES = ['created', 'created_by_ref', 'id', 'type']
 
 TYPE_REGEX = re.compile(r'^\-?[a-z0-9]+(-[a-z0-9]+)*\-?$')
-TYPE_21_REGEX = re.compile(r'([a-z][a-z0-9]*)+(-[a-z0-9]+)*\-?$')
-EXT_21_REGEX = re.compile(r'([a-z][a-z0-9]*)+(-[a-z0-9]+)*\-ext$')
+TYPE_21_REGEX = re.compile(r'^([a-z][a-z0-9]*)+(-[a-z0-9]+)*\-?$')
+EXT_21_REGEX = re.compile(r'^([a-z][a-z0-9]*)+(-[a-z0-9]+)*\-ext$')
 PREFIX_21_REGEX = re.compile(r'^[a-z].*')