diff --git a/reactos/ntoskrnl/ke/i386/trap.s b/reactos/ntoskrnl/ke/i386/trap.s
index ec95b4d6a3a..8d7a809c6c5 100644
--- a/reactos/ntoskrnl/ke/i386/trap.s
+++ b/reactos/ntoskrnl/ke/i386/trap.s
@@ -167,6 +167,9 @@ EXTERN _PsConvertToGuiThread@0:PROC
 
 PUBLIC _KiConvertToGuiThread@0
 _KiConvertToGuiThread@0:
+    /* Safe ebx */
+    push ebx
+
     /* Calculate the stack frame offset in ebx */
     mov ebx, ebp
     sub ebx, esp
@@ -178,6 +181,9 @@ _KiConvertToGuiThread@0:
     mov ebp, esp
     add ebp, ebx
 
+    /* Restore ebx */
+    pop ebx
+
     /* return to the caller */
     ret
 #endif