diff --git a/compiler/rustc_ast/Cargo.toml b/compiler/rustc_ast/Cargo.toml
index 937ee4bcd42..087f6a192b5 100644
--- a/compiler/rustc_ast/Cargo.toml
+++ b/compiler/rustc_ast/Cargo.toml
@@ -4,9 +4,10 @@ version = "0.0.0"
 edition = "2021"
 
 [dependencies]
+# FIXME: bumping memchr to 2.7.1 causes linker errors in MSVC thin-lto
 # tidy-alphabetical-start
 bitflags = "2.4.1"
-memchr = "2.5.0"
+memchr = "=2.5.0"
 rustc_data_structures = { path = "../rustc_data_structures" }
 rustc_index = { path = "../rustc_index" }
 rustc_lexer = { path = "../rustc_lexer" }