diff --git a/util/sis/flash_on.c b/util/sis/flash_on.c
index cfc002a7e4..8432715bab 100644
--- a/util/sis/flash_on.c
+++ b/util/sis/flash_on.c
@@ -49,8 +49,8 @@ main()
 	b = inb(0x0cfc) | 0x0b;
 	outb(b, 0xcfc);
 	/* Flash write enable on SiS 540/630 */
-	outl(0x80000844, 0x0cf8);
-	b = inb(0x0cfd) | 0x40;
+	outl(0x80000845, 0x0cf8);
+	b = inb(0x0cfd) & 0x40;
 	outb(b, 0xcfd);
 
 	/* The same thing on SiS 950 SuperIO side */
diff --git a/util/sis/flash_rom.c b/util/sis/flash_rom.c
index 7620bc99ca..8293c6ec45 100644
--- a/util/sis/flash_rom.c
+++ b/util/sis/flash_rom.c
@@ -67,8 +67,8 @@ int enable_flash_sis630 (void)
     b = inb(0x0cfc) | 0x0b;
     outb(b, 0xcfc);
     /* Flash write enable on SiS 540/630 */
-    outl(0x80000844, 0x0cf8);
-    b = inb(0x0cfd) | 0x40;
+    outl(0x80000845, 0x0cf8);
+    b = inb(0x0cfd) & 0x40;
     outb(b, 0xcfd);
 
     /* The same thing on SiS 950 SuperIO side */