diff --git a/src/hotspot/cpu/aarch64/assembler_aarch64.hpp b/src/hotspot/cpu/aarch64/assembler_aarch64.hpp
index b05c0e800e8..5c0adf45d27 100644
--- a/src/hotspot/cpu/aarch64/assembler_aarch64.hpp
+++ b/src/hotspot/cpu/aarch64/assembler_aarch64.hpp
@@ -2435,6 +2435,7 @@ public:
       break;
     default:
       ShouldNotReachHere();
+      Rm = 0;  // unreachable
     }
 
     starti;