diff --git a/ext/PkgExt.jl b/ext/PkgExt.jl
index 4fc8bd6..d124a2d 100644
--- a/ext/PkgExt.jl
+++ b/ext/PkgExt.jl
@@ -27,7 +27,11 @@ const STACK_SPEC = Pkg.REPLMode.CommandSpec(
 Stack another environment.
 """,
     description = "Stack another environment",
-    completions = Pkg.REPLMode.complete_activate,
+    completions = if VERSION < v"1.11-DEV.0"
+        Pkg.REPLMode.complete_activate
+    else
+        Pkg.REPLMode.get_complete_function(:complete_activate)
+    end,
     should_splat = false,
     arg_count = 0 => Inf)