diff --git a/rustc_codegen_spirv/build_libcore_test.bat b/rustc_codegen_spirv/build_libcore_test.bat
index b86da8143c..d51f0196a1 100644
--- a/rustc_codegen_spirv/build_libcore_test.bat
+++ b/rustc_codegen_spirv/build_libcore_test.bat
@@ -1,7 +1,7 @@
 setlocal
 cargo build
 
-set RUSTFLAGS=-Zcodegen-backend=%cd%/../target/debug/rustc_codegen_spirv.dll -Ccodegen-units=1
+set RUSTFLAGS=-Zcodegen-backend=%cd%/../target/debug/rustc_codegen_spirv.dll
 
 pushd build_libcore_test
 cargo build -Z build-std=core --target spirv-unknown-unknown --release
diff --git a/rustc_codegen_spirv/build_libcore_test.sh b/rustc_codegen_spirv/build_libcore_test.sh
index 83dacd256d..ec90349880 100755
--- a/rustc_codegen_spirv/build_libcore_test.sh
+++ b/rustc_codegen_spirv/build_libcore_test.sh
@@ -6,7 +6,7 @@ set -e
 # build rustc_codegen_spirv
 cargo build
 
-export RUSTFLAGS="-Zcodegen-backend=$PWD/../target/debug/librustc_codegen_spirv.so -Ccodegen-units=1"
+export RUSTFLAGS="-Zcodegen-backend=$PWD/../target/debug/librustc_codegen_spirv.so"
 
 pushd build_libcore_test
 cargo build -Z build-std=core --target spirv-unknown-unknown --release
diff --git a/rustc_codegen_spirv/tests/compile_and_val.rs b/rustc_codegen_spirv/tests/compile_and_val.rs
index 9a97fec097..0f4b8db236 100644
--- a/rustc_codegen_spirv/tests/compile_and_val.rs
+++ b/rustc_codegen_spirv/tests/compile_and_val.rs
@@ -12,7 +12,7 @@ pub fn build_libcore_test() {
         }
     }
     let rustflags = format!(
-        "-Z codegen-backend=librustc_codegen_spirv{} -C codegen-units=1",
+        "-Z codegen-backend=librustc_codegen_spirv{}",
         std::env::consts::DLL_SUFFIX
     );
     let build = Command::new("cargo")