diff --git a/src/libexpr/eval-gc.hh b/src/libexpr/eval-gc.hh
index 1be9ff65b..3b420e418 100644
--- a/src/libexpr/eval-gc.hh
+++ b/src/libexpr/eval-gc.hh
@@ -23,7 +23,8 @@ template<typename T>
 using gc_allocator = std::allocator<T>;
 
 #  define GC_MALLOC_ATOMIC std::malloc
-#  define GC_STRDUP std::strdup
+#  define GC_STRDUP strdup
+
 struct gc
 {};