diff --git a/hal/halx86/generic/cmos.c b/hal/halx86/generic/cmos.c
index 45ad8840956..7e4fb57a6e9 100644
--- a/hal/halx86/generic/cmos.c
+++ b/hal/halx86/generic/cmos.c
@@ -24,8 +24,8 @@ UCHAR
 NTAPI
 HalpReadCmos(IN UCHAR Reg)
 {
-    /* Select the register */
-    WRITE_PORT_UCHAR(CMOS_CONTROL_PORT, Reg);
+    /* Select the register (0x80 to disable NMIs) */
+    WRITE_PORT_UCHAR(CMOS_CONTROL_PORT, 0x80 | Reg);
 
     /* Query the value */
     return READ_PORT_UCHAR(CMOS_DATA_PORT);
@@ -37,8 +37,8 @@ NTAPI
 HalpWriteCmos(IN UCHAR Reg,
               IN UCHAR Value)
 {
-    /* Select the register */
-    WRITE_PORT_UCHAR(CMOS_CONTROL_PORT, Reg);
+    /* Select the register (0x80 to disable NMIs) */
+    WRITE_PORT_UCHAR(CMOS_CONTROL_PORT, 0x80 | Reg);
 
     /* Write the value */
     WRITE_PORT_UCHAR(CMOS_DATA_PORT, Value);