diff --git a/ostd/src/arch/x86/trap/trap.S b/ostd/src/arch/x86/trap/trap.S
index 7ab5ede49..3a3086432 100644
--- a/ostd/src/arch/x86/trap/trap.S
+++ b/ostd/src/arch/x86/trap/trap.S
@@ -57,6 +57,7 @@ trap_handler_table:
 .section .text
 .global trap_common
 trap_common:
+    cld                     # clear DF before calling/returning to any C function to conform to x86-64 calling convention
     push rax
     mov ax, [rsp + 4*8]     # load cs
     and ax, 0x3             # test