diff --git a/src/librustc_target/spec/riscv32imac_unknown_none_elf.rs b/src/librustc_target/spec/riscv32imac_unknown_none_elf.rs
index 5e24f1f1aa2b..8adf562ca7e5 100644
--- a/src/librustc_target/spec/riscv32imac_unknown_none_elf.rs
+++ b/src/librustc_target/spec/riscv32imac_unknown_none_elf.rs
@@ -18,7 +18,7 @@ pub fn target() -> TargetResult {
             linker: Some("rust-lld".to_string()),
             cpu: "generic-rv32".to_string(),
             max_atomic_width: Some(32),
-            atomic_cas: false, // incomplete +a extension
+            atomic_cas: true,
             features: "+m,+a,+c".to_string(),
             executables: true,
             panic_strategy: PanicStrategy::Abort,