diff --git a/os/rt/ports/ARMCMx/compilers/RVCT/chcoreasm_v7m.s b/os/rt/ports/ARMCMx/compilers/RVCT/chcoreasm_v7m.s
index d7ddb1b18..0a974bf42 100644
--- a/os/rt/ports/ARMCMx/compilers/RVCT/chcoreasm_v7m.s
+++ b/os/rt/ports/ARMCMx/compilers/RVCT/chcoreasm_v7m.s
@@ -87,7 +87,7 @@ _port_thread_start PROC
 #if CORTEX_SIMPLIFIED_PRIORITY
                 cpsie   i
 #else
-                movs    r3, #CORTEX_BASEPRI_DISABLED
+                movs    r3, #0              /* CORTEX_BASEPRI_DISABLED */
                 msr     BASEPRI, r3
 #endif
                 mov     r0, r5