diff --git a/opam/opam b/opam/opam
index 3b5bfd175e4f6a47e25746402ad6da257866fbe7..d8f0366beb9887943e65435726e1292afc1441f0 100644
--- a/opam/opam
+++ b/opam/opam
@@ -92,7 +92,7 @@ depends: [
   ( ( "lablgtk" { >= "2.18.2" } & "conf-gnomecanvas" )
   | ( "lablgtk3" { >= "3.0.beta4" } & "lablgtk3-sourceview3"))
   "conf-gtksourceview"
-  "alt-ergo"
+  ( "alt-ergo-free" | "alt-ergo" )
   "conf-graphviz" { post }
 ]