diff --git a/src/libexpr-c/nix_api_expr.cc b/src/libexpr-c/nix_api_expr.cc
index 8f21d702221..333e99460ba 100644
--- a/src/libexpr-c/nix_api_expr.cc
+++ b/src/libexpr-c/nix_api_expr.cc
@@ -16,8 +16,6 @@
 
 #if HAVE_BOEHMGC
 #  include <mutex>
-#  define GC_INCLUDE_NEW 1
-#  include "gc_cpp.h"
 #endif
 
 nix_err nix_libexpr_init(nix_c_context * context)
diff --git a/src/libexpr/eval-gc.hh b/src/libexpr/eval-gc.hh
index 1be9ff65b57..3b420e41867 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
 {};