diff --git a/libc/arch-arm/bionic/tkill.S b/libc/arch-arm/bionic/tkill.S
index fdc5ed4..d5bb739 100644
--- a/libc/arch-arm/bionic/tkill.S
+++ b/libc/arch-arm/bionic/tkill.S
@@ -33,6 +33,7 @@
    of a corrupted malloc heap).
 */
 
+#include <linux/err.h>
 #include <sys/linux-syscalls.h>
 #include <machine/asm.h>
 
@@ -45,7 +46,8 @@
     ldr     r7, =__NR_tkill
     swi     #0
     ldmfd   sp!, {r4-r7, ip, lr}
-    movs    r0, r0
-    bxpl    lr
-    b       __set_syscall_errno
+    cmn     r0, #(MAX_ERRNO + 1)
+    bxls    lr
+    neg     r0, r0
+    b       __set_errno
 END(tkill)