diff --git a/src/esx/esx_vi_generator.py b/src/esx/esx_vi_generator.py
index 95521fa1e52b9edcdf0505739c1daf63daa1eb39..df913d89150cf731bb122a65623566f298b67adc 100755
--- a/src/esx/esx_vi_generator.py
+++ b/src/esx/esx_vi_generator.py
@@ -75,16 +75,17 @@ class Member:
 
 
     def get_occurrence_comment(self):
-        if self.occurrence == OCCURRENCE__REQUIRED_ITEM:
-            return "/* required */"
-        elif self.occurrence == OCCURRENCE__REQUIRED_LIST:
-            return "/* required, list */"
-        elif self.occurrence == OCCURRENCE__OPTIONAL_ITEM:
-            return "/* optional */"
-        elif self.occurrence == OCCURRENCE__OPTIONAL_LIST:
-            return "/* optional, list */"
+        occurrence_map = {
+            OCCURRENCE__REQUIRED_ITEM: "/* required */",
+            OCCURRENCE__REQUIRED_LIST: "/* required, list */",
+            OCCURRENCE__OPTIONAL_ITEM: "/* optional */",
+            OCCURRENCE__OPTIONAL_LIST: "/* optional, list */"
+        }
+        try:
+            return occurrence_map[self.occurrence]
+        except KeyError:
+            raise ValueError("unknown occurrence value '%s'" % self.occurrence)
 
-        raise ValueError("unknown occurrence value '%s'" % self.occurrence)