diff --git a/reactos/lib/fast486/common.inl b/reactos/lib/fast486/common.inl
index 084bf1e2288..381ed032cdc 100644
--- a/reactos/lib/fast486/common.inl
+++ b/reactos/lib/fast486/common.inl
@@ -112,13 +112,12 @@ Fast486GetPageTableEntry(PFAST486_STATE State,
     /* Make sure it is present */
     if (!TableEntry.Present) return 0;
 
-    if (MarkAsDirty) TableEntry.Dirty = TRUE;
-
-    /* Was the table entry accessed before? */
-    if (!TableEntry.Accessed)
+    /* Do we need to change any flags? */
+    if (!TableEntry.Accessed || (MarkAsDirty && !TableEntry.Dirty))
     {
-        /* Well, it is now */
+        /* Mark it as accessed and optionally dirty too */
         TableEntry.Accessed = TRUE;
+        if (MarkAsDirty) TableEntry.Dirty = TRUE;
 
         /* Write back the table entry */
         State->MemWriteCallback(State,
@@ -512,6 +511,7 @@ Fast486LoadSegmentInternal(PFAST486_STATE State,
         {
             /* Invalid selector */
             Fast486ExceptionWithErrorCode(State, Exception, Selector);
+            return FALSE;
         }
 
         if (Segment == FAST486_REG_SS)
@@ -569,6 +569,7 @@ Fast486LoadSegmentInternal(PFAST486_STATE State,
             {
                 /* Must be a segment descriptor */
                 Fast486ExceptionWithErrorCode(State, Exception, Selector);
+                return FALSE;
             }
 
             if (!GdtEntry.Present)
diff --git a/reactos/lib/fast486/fpu.h b/reactos/lib/fast486/fpu.h
index b23c795d32b..056ef8335d2 100644
--- a/reactos/lib/fast486/fpu.h
+++ b/reactos/lib/fast486/fpu.h
@@ -28,7 +28,7 @@
 
 /* DEFINES ********************************************************************/
 
-#define FPU_CHECK() if (State->ControlRegisters[FAST486_REG_CR0] & FAST486_CR0_EM) \
+#define FPU_CHECK() if (State->ControlRegisters[FAST486_REG_CR0] & (FAST486_CR0_EM | FAST486_CR0_TS)) \
                     { \
                         Fast486Exception(State, FAST486_EXCEPTION_NM); \
                         return; \