diff --git a/src/arch/x86_64/boot.asm b/src/arch/x86_64/boot.asm
index 663e9e09..2f58d53f 100644
--- a/src/arch/x86_64/boot.asm
+++ b/src/arch/x86_64/boot.asm
@@ -116,10 +116,10 @@ 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"