diff --git a/tools/apidoc/gen_toc.py b/tools/apidoc/gen_toc.py
index 0b0702ac86c..84140eefadb 100644
--- a/tools/apidoc/gen_toc.py
+++ b/tools/apidoc/gen_toc.py
@@ -248,10 +248,10 @@ for f in sys.argv:
 
 def xml_for(command):
     name = command['name']
-    async = command['async'] and ' (A)' or ''
+    isAsync = command['async'] and ' (A)' or ''
     dirname = command['dirname']
     return '''<xsl:if test="name=\'%(name)s\'">
-<li><a href="%(dirname)s/%(name)s.html"><xsl:value-of select="name"/>%(async)s</a></li>
+<li><a href="%(dirname)s/%(name)s.html"><xsl:value-of select="name"/>%(isAsync)s</a></li>
 </xsl:if>
 ''' % locals()