diff --git a/arch/i386/kernel/traps.c b/arch/i386/kernel/traps.c
index a61f33d06ea34313b9a36a271d9fd69f2b2034db..cd2d5d5514fe0ffcdf78cadfbabdf5863ede040c 100644
--- a/arch/i386/kernel/traps.c
+++ b/arch/i386/kernel/traps.c
@@ -803,15 +803,17 @@ void math_error(void __user *eip)
 	 */
 	cwd = get_fpu_cwd(task);
 	swd = get_fpu_swd(task);
-	switch (((~cwd) & swd & 0x3f) | (swd & 0x240)) {
+	switch (swd & ~cwd & 0x3f) {
 		case 0x000:
 		default:
 			break;
 		case 0x001: /* Invalid Op */
-		case 0x041: /* Stack Fault */
-		case 0x241: /* Stack Fault | Direction */
+			/*
+			 * swd & 0x240 == 0x040: Stack Underflow
+			 * swd & 0x240 == 0x240: Stack Overflow
+			 * User must clear the SF bit (0x40) if set
+			 */
 			info.si_code = FPE_FLTINV;
-			/* Should we clear the SF or let user space do it ???? */
 			break;
 		case 0x002: /* Denormalize */
 		case 0x010: /* Underflow */