diff --git a/src/nix/repl.cc b/src/nix/repl.cc
index e9bebff17..2c39fac91 100644
--- a/src/nix/repl.cc
+++ b/src/nix/repl.cc
@@ -623,6 +623,9 @@ void NixRepl::loadFile(const Path & path)
 
 void NixRepl::loadFlake(const std::string & flakeRefS)
 {
+    if (flakeRefS.empty())
+        throw Error("cannot use ':load-flake' without a path specified. (Use '.' for the current working directory.)");
+
     auto flakeRef = parseFlakeRef(flakeRefS, absPath("."), true);
     if (evalSettings.pureEval && !flakeRef.input.isImmutable())
         throw Error("cannot use ':load-flake' on mutable flake reference '%s' (use --impure to override)", flakeRefS);