diff --git a/_posts/2015-08-25-entering-longmode.md b/_posts/2015-08-25-entering-longmode.md
index 0621dea0..72f4de6c 100644
--- a/_posts/2015-08-25-entering-longmode.md
+++ b/_posts/2015-08-25-entering-longmode.md
@@ -125,10 +125,10 @@ test_long_mode:
     cpuid                  ; CPU identification.
     cmp eax, 0x80000001    ; Compare the A-register with 0x80000001.
     jb .no_long_mode       ; It is less, there is no long mode.
-    mov eax, 0x80000000    ; Set the A-register to 0x80000000.
+    mov eax, 0x80000001    ; Set the A-register to 0x80000001.
     cpuid                  ; CPU identification.
-    cmp eax, 0x80000001    ; Compare the A-register with 0x80000001.
-    jb .no_long_mode       ; It is less, there is no long mode.
+    test edx, 1 << 29      ; Test if the LM-bit, which is bit 29, is set in the D-register.
+    jz .no_long_mode       ; They aren't, there is no long mode.
     ret
 .no_long_mode:
     mov al, "2"