diff --git a/src/runtime/proc.go b/src/runtime/proc.go
index 0fa0cf965e6d2..1ad95ae9a6eb0 100644
--- a/src/runtime/proc.go
+++ b/src/runtime/proc.go
@@ -518,7 +518,7 @@ func dumpgstatus(gp *g) {
 
 func checkmcount() {
 	// sched lock is held
-	if sched.mcount > sched.maxmcount {
+	if mcount() > sched.maxmcount {
 		print("runtime: program exceeds ", sched.maxmcount, "-thread limit\n")
 		throw("thread exhaustion")
 	}
@@ -533,8 +533,11 @@ func mcommoninit(mp *m) {
 	}
 
 	lock(&sched.lock)
-	mp.id = sched.mcount
-	sched.mcount++
+	if sched.mnext+1 < sched.mnext {
+		throw("runtime: thread ID overflow")
+	}
+	mp.id = sched.mnext
+	sched.mnext++
 	checkmcount()
 
 	mp.fastrand[0] = 1597334677 * uint32(mp.id)
@@ -3374,7 +3377,7 @@ func gcount() int32 {
 }
 
 func mcount() int32 {
-	return sched.mcount
+	return int32(sched.mnext)
 }
 
 var prof struct {
@@ -3854,7 +3857,7 @@ func acquirep1(_p_ *p) {
 		throw("acquirep: already in go")
 	}
 	if _p_.m != 0 || _p_.status != _Pidle {
-		id := int32(0)
+		id := int64(0)
 		if _p_.m != 0 {
 			id = _p_.m.ptr().id
 		}
@@ -3915,12 +3918,12 @@ func checkdead() {
 		return
 	}
 
-	run := sched.mcount - sched.nmidle - sched.nmidlelocked - sched.nmsys
+	run := mcount() - sched.nmidle - sched.nmidlelocked - sched.nmsys
 	if run > 0 {
 		return
 	}
 	if run < 0 {
-		print("runtime: checkdead: nmidle=", sched.nmidle, " nmidlelocked=", sched.nmidlelocked, " mcount=", sched.mcount, " nmsys=", sched.nmsys, "\n")
+		print("runtime: checkdead: nmidle=", sched.nmidle, " nmidlelocked=", sched.nmidlelocked, " mcount=", mcount(), " nmsys=", sched.nmsys, "\n")
 		throw("checkdead: inconsistent counts")
 	}
 
@@ -4234,7 +4237,7 @@ func schedtrace(detailed bool) {
 	}
 
 	lock(&sched.lock)
-	print("SCHED ", (now-starttime)/1e6, "ms: gomaxprocs=", gomaxprocs, " idleprocs=", sched.npidle, " threads=", sched.mcount, " spinningthreads=", sched.nmspinning, " idlethreads=", sched.nmidle, " runqueue=", sched.runqsize)
+	print("SCHED ", (now-starttime)/1e6, "ms: gomaxprocs=", gomaxprocs, " idleprocs=", sched.npidle, " threads=", mcount(), " spinningthreads=", sched.nmspinning, " idlethreads=", sched.nmidle, " runqueue=", sched.runqsize)
 	if detailed {
 		print(" gcwaiting=", sched.gcwaiting, " nmidlelocked=", sched.nmidlelocked, " stopwait=", sched.stopwait, " sysmonwait=", sched.sysmonwait, "\n")
 	}
@@ -4246,7 +4249,7 @@ func schedtrace(detailed bool) {
 		h := atomic.Load(&_p_.runqhead)
 		t := atomic.Load(&_p_.runqtail)
 		if detailed {
-			id := int32(-1)
+			id := int64(-1)
 			if mp != nil {
 				id = mp.id
 			}
@@ -4294,11 +4297,11 @@ func schedtrace(detailed bool) {
 		gp := allgs[gi]
 		mp := gp.m
 		lockedm := gp.lockedm.ptr()
-		id1 := int32(-1)
+		id1 := int64(-1)
 		if mp != nil {
 			id1 = mp.id
 		}
-		id2 := int32(-1)
+		id2 := int64(-1)
 		if lockedm != nil {
 			id2 = lockedm.id
 		}
diff --git a/src/runtime/runtime2.go b/src/runtime/runtime2.go
index 3f99de65d563c..e652f5be64987 100644
--- a/src/runtime/runtime2.go
+++ b/src/runtime/runtime2.go
@@ -399,7 +399,7 @@ type m struct {
 	caughtsig     guintptr // goroutine running during fatal signal
 	p             puintptr // attached p for executing go code (nil if not executing go code)
 	nextp         puintptr
-	id            int32
+	id            int64
 	mallocing     int32
 	throwing      int32
 	preemptoff    string // if != "", keep curg running on this m
@@ -531,7 +531,7 @@ type schedt struct {
 	midle        muintptr // idle m's waiting for work
 	nmidle       int32    // number of idle m's waiting for work
 	nmidlelocked int32    // number of locked m's waiting for work
-	mcount       int32    // number of m's that have been created
+	mnext        int64    // number of m's that have been created and next M ID
 	maxmcount    int32    // maximum number of m's allowed (or die)
 	nmsys        int32    // number of system m's not counted for deadlock
 
diff --git a/src/runtime/signal_sighandler.go b/src/runtime/signal_sighandler.go
index 672d7828ff677..f24a117fcdf56 100644
--- a/src/runtime/signal_sighandler.go
+++ b/src/runtime/signal_sighandler.go
@@ -111,7 +111,7 @@ func sighandler(sig uint32, info *siginfo, ctxt unsafe.Pointer, gp *g) {
 
 	if docrash {
 		crashing++
-		if crashing < sched.mcount-int32(extraMCount) {
+		if crashing < mcount()-int32(extraMCount) {
 			// There are other m's that need to dump their stacks.
 			// Relay SIGQUIT to the next m by sending it to the current process.
 			// All m's that have already received SIGQUIT have signal masks blocking