--- a/toolkit/library/rust/shared/build.rs
+++ b/toolkit/library/rust/shared/build.rs
@@ -7,17 +7,19 @@ fn main() {
     let mut bootstrap = false;
 
     if ver >= Version::parse("1.24.0").unwrap() && ver < Version::parse("1.27.0").unwrap() {
         println!("cargo:rustc-cfg=feature=\"oom_with_global_alloc\"");
         bootstrap = true;
     } else if ver >= Version::parse("1.28.0-alpha").unwrap() && ver < Version::parse("1.29.0").unwrap() {
         println!("cargo:rustc-cfg=feature=\"oom_with_hook\"");
         bootstrap = true;
-    } else if std::env::var("MOZ_AUTOMATION").is_ok() {
+    } else if std::env::var("MOZ_AUTOMATION").is_ok() && ver >= Version::parse("1.29.0-alpha").unwrap() {
+        // For the sake of the base-toolchains build we allow building with 1.27, but
+        // retain this check for newer versions.
         panic!("Builds on automation must use a version of rust that supports OOM hooking")
     }
 
     // This is a rather awful thing to do, but we're only doing it on
     // versions of rustc that are not going to change the unstable APIs
     // we use from under us, all being already released or beta.
     if bootstrap {
         println!("cargo:rustc-env=RUSTC_BOOTSTRAP=1");