diff --git a/x86/access.c b/x86/access.c
index a0c19dc..11f561b 100644
--- a/x86/access.c
+++ b/x86/access.c
@@ -207,7 +207,7 @@
     if (smep)
         ptl2[2] &= ~PT_USER_MASK;
     r = write_cr4_checking(cr4);
-    if (!smep)
+    if (r || !smep)
         ptl2[2] |= PT_USER_MASK;
     return r;
 }