diff --git a/gtkdoc-mkdb.in b/gtkdoc-mkdb.in
index de0d35d..276b163 100755
--- a/gtkdoc-mkdb.in
+++ b/gtkdoc-mkdb.in
@@ -1091,11 +1091,12 @@ sub OutputIndex {
 
     @TRACE@("generate $basename index (".%apiindex." entries)\n");
 
-    # do a case insensitive sort while chopping off the prefix
+    # do a case insensitive sort while chopping off the prefix. we sort case
+    # sensitively first to ensure a deterministic order within this.
     foreach my $hash (
         sort { $$a{criteria} cmp $$b{criteria} }
         map { my $x = uc($_); $x =~ s/^$NAME_SPACE\_?(.*)/$1/i; { criteria => $x, original => $_, short => $1 } }
-        keys %apiindex) {
+        sort keys %apiindex) {
 
         $symbol = $$hash{original};
         if (defined($$hash{short})) {