diff --git a/src/nix-env/nix-env.cc b/src/nix-env/nix-env.cc
index a43b103f6..f9c8a8d31 100644
--- a/src/nix-env/nix-env.cc
+++ b/src/nix-env/nix-env.cc
@@ -150,10 +150,8 @@ static void loadSourceExpr(EvalState & state, const Path & path, Value & v)
     if (stat(path.c_str(), &st) == -1)
         throw SysError(format("getting information about '%1%'") % path);
 
-    if (isNixExpr(path, st)) {
+    if (isNixExpr(path, st))
         state.evalFile(path, v);
-        return;
-    }
 
     /* The path is a directory.  Put the Nix expressions in the
        directory in a set, with the file name of each expression as
@@ -161,13 +159,15 @@ static void loadSourceExpr(EvalState & state, const Path & path, Value & v)
        set flat, not nested, to make it easier for a user to have a
        ~/.nix-defexpr directory that includes some system-wide
        directory). */
-    if (S_ISDIR(st.st_mode)) {
+    else if (S_ISDIR(st.st_mode)) {
         state.mkAttrs(v, 1024);
         state.mkList(*state.allocAttr(v, state.symbols.create("_combineChannels")), 0);
         StringSet attrs;
         getAllExprs(state, path, attrs, v);
         v.attrs->sort();
     }
+
+    else throw Error("path '%s' is not a directory or a Nix expression", path);
 }