diff --git a/src/libexpr/primops.cc b/src/libexpr/primops.cc
index f66b24b770..149c7ca399 100644
--- a/src/libexpr/primops.cc
+++ b/src/libexpr/primops.cc
@@ -183,8 +183,8 @@ static void prim_genericClosure(EvalState & state, Value * * args, Value & v)
     list<Value> res;
     set<Value, CompareValues> doneKeys; // !!! use Value *?
     while (!workSet.empty()) {
-	Value * e = *(workSet.begin());
-	workSet.pop_front();
+        Value * e = *(workSet.begin());
+        workSet.pop_front();
 
         state.forceAttrs(*e);
 
@@ -1032,7 +1032,10 @@ static void prim_div(EvalState & state, Value * * args, Value & v)
 
 static void prim_lessThan(EvalState & state, Value * * args, Value & v)
 {
-    mkBool(v, state.forceInt(*args[0]) < state.forceInt(*args[1]));
+    state.forceValue(*args[0]);
+    state.forceValue(*args[1]);
+    CompareValues comp;
+    mkBool(v, comp(*args[0], *args[1]));
 }
 
 
diff --git a/tests/lang/eval-okay-arithmetic.exp b/tests/lang/eval-okay-arithmetic.exp
index d73ac3eb70..b195055b7a 100644
--- a/tests/lang/eval-okay-arithmetic.exp
+++ b/tests/lang/eval-okay-arithmetic.exp
@@ -1 +1 @@
-2185
+2188
diff --git a/tests/lang/eval-okay-arithmetic.nix b/tests/lang/eval-okay-arithmetic.nix
index 62a0ada065..8f307b20ea 100644
--- a/tests/lang/eval-okay-arithmetic.nix
+++ b/tests/lang/eval-okay-arithmetic.nix
@@ -50,6 +50,11 @@ let {
       (if 2 > 1 == 1 < 2 then 1 else err)
       (if 1 + 2 * 3 >= 7 then 1 else err)
       (if 1 + 2 * 3 < 7 then err else 1)
+
+      # Not integer, but so what.
+      (if "aa" < "ab" then 1 else err)
+      (if "aa" < "aa" then err else 1)
+      (if "foo" < "foobar" then 1 else err)
     ];
 
 }