diff --git a/crates/proc-macro-srv/Cargo.toml b/crates/proc-macro-srv/Cargo.toml
index 54dae4eba9..ba17ea6f7b 100644
--- a/crates/proc-macro-srv/Cargo.toml
+++ b/crates/proc-macro-srv/Cargo.toml
@@ -38,7 +38,7 @@ proc-macro-test.path = "./proc-macro-test"
 
 [features]
 sysroot-abi = []
-in-rust-tree = ["mbe/in-rust-tree"]
+in-rust-tree = ["mbe/in-rust-tree", "sysroot-abi"]
 
 [lints]
 workspace = true