diff --git a/conf_sample.py b/conf_sample.py
index 0520969..1cc2670 100644
--- a/conf_sample.py
+++ b/conf_sample.py
@@ -9,3 +9,4 @@
 
 UMLS_VERSION = "2011ab"
 
+UMLS_BASE_URI = "http://purl.bioontology.org/ontology/"
diff --git a/umls2rdf.py b/umls2rdf.py
index aad95b2..33e3fc0 100755
--- a/umls2rdf.py
+++ b/umls2rdf.py
@@ -83,7 +83,7 @@
 MRSAB_LAT = 19
 
 def get_umls_url(code):
-    return "http://purl.bioontology.org/ontology/%s/"%code
+    return "%s%s/"%(conf.UMLS_BASE_URI,code)
 
 def flatten(matrix):
     return reduce(lambda x,y: x+y,matrix)