diff --git a/boot/startup32.S b/boot/startup32.S
index 5059ba6..ca5535a 100644
--- a/boot/startup32.S
+++ b/boot/startup32.S
@@ -744,7 +744,7 @@ ap_trampoline:
 	movl	%edi, %eax
 	addl	$(gdt - startup), %eax
 	movl	%eax, (ap_gdt_descr - ap_trampoline + 2)
-	lgdt	ap_gdt_descr - ap_trampoline
+data32	lgdt	ap_gdt_descr - ap_trampoline
 
 	# Switch to protected mode and reload the segment registers.
 
diff --git a/boot/startup64.S b/boot/startup64.S
index d0cd704..a6f86d1 100644
--- a/boot/startup64.S
+++ b/boot/startup64.S
@@ -556,7 +556,7 @@ ap_trampoline:
 	movl	%ebx, %eax
 	addl	$(gdt - startup), %eax
 	movl	%eax, (ap_gdt_descr - ap_trampoline + 2)
-	lgdt	ap_gdt_descr - ap_trampoline
+data32	lgdt	ap_gdt_descr - ap_trampoline
 
 	# Set the page directory base address.