Revert "Prevent config.h from being clobbered"

This reverts commit 28bba8c44f484eae38e8a15dcec73cfa999156f6.

1 files changed, 1 insertions, 1 deletions

diff --git a/src/libexpr/eval.cc b/src/libexpr/eval.cc
index 676dd3ac461a..a1613a4205b4 100644
--- a/src/libexpr/eval.cc
+++ b/src/libexpr/eval.cc
@@ -966,7 +966,7 @@ void ExprConcatStrings::eval(EvalState & state, Env & env, Value & v)
            since paths are copied when they are used in a derivation),
            and none of the strings are allowed to have contexts. */
         if (first) {
-            isPath = vStr.type == tPath;
+            isPath = !forceString && vStr.type == tPath;
             first = false;
         }