diff --git a/arch/um/kernel/skas/syscall.c b/arch/um/kernel/skas/syscall.c
index 0728fee..b783ac8 100644
--- a/arch/um/kernel/skas/syscall.c
+++ b/arch/um/kernel/skas/syscall.c
@@ -27,12 +27,7 @@
 	if (secure_computing(NULL) == -1)
 		goto out;
 
-	/* Update the syscall number after orig_ax has potentially been updated
-	 * with ptrace.
-	 */
-	UPT_SYSCALL_NR(r) = PT_SYSCALL_NR(r->gp);
 	syscall = UPT_SYSCALL_NR(r);
-
 	if (syscall >= 0 && syscall <= __NR_syscall_max)
 		PT_REGS_SET_SYSCALL_RETURN(regs,
 				EXECUTE_SYSCALL(syscall, regs));
diff --git a/arch/x86/um/ptrace_32.c b/arch/x86/um/ptrace_32.c
index ebd4dd6..a7ef7b1 100644
--- a/arch/x86/um/ptrace_32.c
+++ b/arch/x86/um/ptrace_32.c
@@ -84,7 +84,10 @@
 	case EAX:
 	case EIP:
 	case UESP:
+		break;
 	case ORIG_EAX:
+		/* Update the syscall number. */
+		UPT_SYSCALL_NR(&child->thread.regs.regs) = value;
 		break;
 	case FS:
 		if (value && (value & 3) != 3)
diff --git a/arch/x86/um/ptrace_64.c b/arch/x86/um/ptrace_64.c
index faab418..0b5c184 100644
--- a/arch/x86/um/ptrace_64.c
+++ b/arch/x86/um/ptrace_64.c
@@ -78,7 +78,11 @@
 	case RSI:
 	case RDI:
 	case RBP:
+		break;
+
 	case ORIG_RAX:
+		/* Update the syscall number. */
+		UPT_SYSCALL_NR(&child->thread.regs.regs) = value;
 		break;
 
 	case FS: