diff --git a/sys/kern/sys_process.c b/sys/kern/sys_process.c
index 7a0c02ea01e..636d10bdba0 100644
--- a/sys/kern/sys_process.c
+++ b/sys/kern/sys_process.c
@@ -522,11 +522,13 @@ kern_ptrace(struct thread *td, int req, pid_t pid, void *addr, int data)
 
 		switch (req) {
 		case PT_STEP:
+			PROC_UNLOCK(p);
 			error = ptrace_single_step(td2);
 			if (error) {
-				_PRELE(p);
-				goto fail;
+				PRELE(p);
+				goto fail_noproc;
 			}
+			PROC_LOCK(p);
 			break;
 		case PT_TO_SCE:
 			p->p_stops |= S_PT_SCE;
@@ -540,11 +542,13 @@ kern_ptrace(struct thread *td, int req, pid_t pid, void *addr, int data)
 		}
 
 		if (addr != (void *)1) {
+			PROC_UNLOCK(p);
 			error = ptrace_set_pc(td2, (u_long)(uintfptr_t)addr);
 			if (error) {
-				_PRELE(p);
-				goto fail;
+				PRELE(p);
+				goto fail_noproc;
 			}
+			PROC_LOCK(p);
 		}
 		_PRELE(p);
 
@@ -705,9 +709,9 @@ kern_ptrace(struct thread *td, int req, pid_t pid, void *addr, int data)
 #ifdef __HAVE_PTRACE_MACHDEP
 		if (req >= PT_FIRSTMACH) {
 			_PHOLD(p);
-			error = cpu_ptrace(td2, req, addr, data);
-			_PRELE(p);
 			PROC_UNLOCK(p);
+			error = cpu_ptrace(td2, req, addr, data);
+			PRELE(p);
 			return (error);
 		}
 #endif
@@ -719,6 +723,7 @@ kern_ptrace(struct thread *td, int req, pid_t pid, void *addr, int data)
 
 fail:
 	PROC_UNLOCK(p);
+fail_noproc:
 	if (proctree_locked)
 		sx_xunlock(&proctree_lock);
 	return (error);
diff --git a/sys/kern/syscalls.master b/sys/kern/syscalls.master
index f23f05607a3..aa9c9696bba 100644
--- a/sys/kern/syscalls.master
+++ b/sys/kern/syscalls.master
@@ -76,7 +76,7 @@
 23	MSTD	{ int setuid(uid_t uid); }
 24	MSTD	{ uid_t getuid(void); }
 25	MSTD	{ uid_t geteuid(void); }
-26	STD	{ int ptrace(int req, pid_t pid, caddr_t addr, int data); }
+26	MSTD	{ int ptrace(int req, pid_t pid, caddr_t addr, int data); }
 27	MSTD	{ int recvmsg(int s, struct msghdr *msg, int flags); }
 28	MSTD	{ int sendmsg(int s, struct msghdr *msg, int flags); }
 29	MSTD	{ int recvfrom(int s, caddr_t buf, size_t len, int flags, \