diff --git a/bin/check-reference-configuration.sh b/bin/check-reference-configuration.sh
index 6557c2eca7defd285aebdb24afa512ccad39385e..e91365642881b711352f863c119deecc00de901e 100755
--- a/bin/check-reference-configuration.sh
+++ b/bin/check-reference-configuration.sh
@@ -7,6 +7,17 @@ if ! type "opam" > /dev/null; then
     opam="NOT"
 else
     opam="$(opam --version)"
+    if [[ $opam =~ ^([0-9+]).([0-9+]) ]]; then
+        major="${BASH_REMATCH[1]}"
+        minor="${BASH_REMATCH[2]}"
+        if [[ "$major" -eq 2 && "$minor" -eq 0 ]]; then
+            echo "warning: opam > 2.1 expected, got $major.$minor."
+            echo "         Suggested commands may not work properly."
+        fi
+    else
+        echo "warning: unknown opam version."
+        echo "         Suggested commands may not work properly."
+    fi
 fi
 
 if ! type "ocaml" > /dev/null; then
@@ -63,7 +74,6 @@ echo "All packages checked."
 if [ $has_any_diffs -ne 0 ]; then
     echo "Useful commands:"
     echo "    opam switch create ${working_ocaml}"
-    echo "    opam install depext"
-    echo "    opam depext --install$all_packages"
+    echo "    opam install$all_packages"
     echo "    rm -f ~/.why3.conf && why3 config detect"
 fi
diff --git a/reference-configuration.md b/reference-configuration.md
index 0e7e1ad675ab498a57e813eaea8d8902163d097b..230a167885f83de851a73c69ebce1375484b990c 100644
--- a/reference-configuration.md
+++ b/reference-configuration.md
@@ -7,18 +7,17 @@ support libraries (notably gtksourceview). lablgtk3 should be preferred.
 
 - OCaml 4.08.1
 - alt-ergo.2.2.0 (for wp, optional)
-- apron.v0.9.12 (for eva, optional)
+- apron.v0.9.13 (for eva, optional)
 - coq.8.13.0 (for wp, optional)
 - lablgtk3.3.1.1 + lablgtk3-sourceview3.3.1.1 | lablgtk.2.18.11
-- mlgmpidl.1.2.12 (for eva, optional)
+- mlgmpidl.1.2.14 (for eva, optional)
 - ocamlfind.1.8.1
 - ocamlgraph.1.8.8
 - ppx_deriving_yojson.3.6.1 (for mdr, optional)
-- ppx_import.1.9.0
+- ppx_import.1.9.1
 - why3.1.4.0
 - yojson.1.7.0
-- zarith.1.10
-- zmq.5.1.3 (for server, optional)
+- zarith.1.12
 
 [^gcc-10]: As mentioned in this [OCaml PR](https://github.com/ocaml/ocaml/issues/9144)
 gcc 10 changed its default linking conventions to make them more stringent,