diff --git a/src/coalg/coalg.ml b/src/coalg/coalg.ml
index 2bfbf206c16f339affdb9ead83fd1fa5522404e6..25df277e58c6df6fdfcf1e16a0139b3fc472dce8 100644
--- a/src/coalg/coalg.ml
+++ b/src/coalg/coalg.ml
@@ -94,9 +94,12 @@ let verbose = ref false
 let choiceSat () =
     let verb = !verbose in
     let sorts = (FE.sortTableFromString Sys.argv.(2)) in
-    if Array.exists (fun (func,_) -> func == CM.GML || func == CM.PML) sorts then
+
+    (* test if GML or PML occurs in sort table *)
+    if Array.fold_left (fun x (func,_) -> x || func == CM.GML || func == CM.PML) false sorts then
       raise (CF.CoAlgException "GML and PML are currently not supported")
     else ();
+
     let printRes sat =
       if not verb then
         print_endline (if sat then "satisfiable\n" else "unsatisfiable\n")