diff --git a/runtime/arch/x86/quick_entrypoints_x86.S b/runtime/arch/x86/quick_entrypoints_x86.S
index 336a0cc..fd2cfeb 100644
--- a/runtime/arch/x86/quick_entrypoints_x86.S
+++ b/runtime/arch/x86/quick_entrypoints_x86.S
@@ -561,8 +561,8 @@
     jz   .Lslow_unlock
     movl LOCK_WORD_OFFSET(%eax), %ecx     // ecx := lock word
     movl %fs:THREAD_ID_OFFSET, %edx       // edx := thread id
-    test %ecx, %ecx
-    jb   .Lslow_unlock                    // lock word contains a monitor
+    test LITERAL(0xC0000000), %ecx
+    jnz  .Lslow_unlock                    // lock word contains a monitor
     cmpw %cx, %dx                         // does the thread id match?
     jne  .Lslow_unlock
     cmpl LITERAL(65536), %ecx