diff --git a/bazel/cc_toolchains/clang_cc_toolchain_config.bzl b/bazel/cc_toolchains/clang_cc_toolchain_config.bzl
index a7f7d96fb3e0..9330a302adb3 100644
--- a/bazel/cc_toolchains/clang_cc_toolchain_config.bzl
+++ b/bazel/cc_toolchains/clang_cc_toolchain_config.bzl
@@ -528,11 +528,10 @@ def _impl(ctx):
                 actions = all_compile_actions,
                 flag_groups = [flag_group(flags = [
                     # Enable libc++'s debug features.
-                    "-D_LIBCXX_DEBUG=1",
+                    "-D_LIBCPP_DEBUG=1",
                 ])],
                 with_features = [
-                    with_feature_set(features = ["dbg"]),
-                    with_feature_set(features = ["fastbuild"]),
+                    with_feature_set(not_features = ["opt"]),
                 ],
             ),
         ],