diff --git a/tools/graphgen/graphGen_arg.ml b/tools/graphgen/graphGen_arg.ml
index 73d53eb7d804c5899127fa4953da6093a7dd229e..177acc5704d094459c07edc6c88f02128a684334 100644
--- a/tools/graphgen/graphGen_arg.ml
+++ b/tools/graphgen/graphGen_arg.ml
@@ -241,7 +241,7 @@ let (mkoptab : string array -> t -> unit) =
       [(["Set the second radius around all nodes.";
          "2 by default.\n"],"QUDG")];
 
-    mkopt args ["--probability";"-p"]~arg:" <float>"
+    mkopt args ["--probability"]~arg:" <float>"
       (Arg.Float (fun p -> args.qudg.p <- p))
       [(["Sets the probability of the nodes being neighbors when they are ";
            "inside the second";