diff --git a/src/runtime/malloc.go b/src/runtime/malloc.go
index 7affe244a25..c389cb1e45c 100644
--- a/src/runtime/malloc.go
+++ b/src/runtime/malloc.go
@@ -1301,7 +1301,7 @@ func fastexprand(mean int) int32 {
 	// x = -log_e(q) * mean
 	// x = log_2(q) * (-log_e(2)) * mean    ; Using log_2 for efficiency
 	const randomBitCount = 26
-	q := fastrand()%(1<<randomBitCount) + 1
+	q := fastrandn(1<<randomBitCount) + 1
 	qlog := fastlog2(float64(q)) - randomBitCount
 	if qlog > 0 {
 		qlog = 0
@@ -1319,7 +1319,7 @@ func nextSampleNoFP() uintptr {
 		rate = 0x3fffffff
 	}
 	if rate != 0 {
-		return uintptr(fastrand() % uint32(2*rate))
+		return uintptr(fastrandn(uint32(2 * rate)))
 	}
 	return 0
 }
diff --git a/src/runtime/mbitmap.go b/src/runtime/mbitmap.go
index 9363409e361..daf1fcfbc09 100644
--- a/src/runtime/mbitmap.go
+++ b/src/runtime/mbitmap.go
@@ -974,7 +974,7 @@ func heapBitsSetType(x, size, dataSize uintptr, typ *_type) {
 	// machine instructions.
 
 	outOfPlace := false
-	if arenaIndex(x+size-1) != arenaIdx(h.arena) || (doubleCheck && fastrand()%2 == 0) {
+	if arenaIndex(x+size-1) != arenaIdx(h.arena) || (doubleCheck && fastrandn(2) == 0) {
 		// This object spans heap arenas, so the bitmap may be
 		// discontiguous. Unroll it into the object instead
 		// and then copy it out.
diff --git a/src/runtime/proc.go b/src/runtime/proc.go
index aa2ba96c8f7..c14a1f143c7 100644
--- a/src/runtime/proc.go
+++ b/src/runtime/proc.go
@@ -5840,7 +5840,7 @@ const randomizeScheduler = raceenabled
 // If the run queue is full, runnext puts g on the global queue.
 // Executed only by the owner P.
 func runqput(_p_ *p, gp *g, next bool) {
-	if randomizeScheduler && next && fastrand()%2 == 0 {
+	if randomizeScheduler && next && fastrandn(2) == 0 {
 		next = false
 	}
 
diff --git a/src/runtime/stubs.go b/src/runtime/stubs.go
index 91380a0d513..ad78363bb67 100644
--- a/src/runtime/stubs.go
+++ b/src/runtime/stubs.go
@@ -156,8 +156,8 @@ func fastrandn(n uint32) uint32 {
 	return uint32(uint64(fastrand()) * uint64(n) >> 32)
 }
 
-//go:linkname sync_fastrand sync.fastrand
-func sync_fastrand() uint32 { return fastrand() }
+//go:linkname sync_fastrandn sync.fastrandn
+func sync_fastrandn(n uint32) uint32 { return fastrandn(n) }
 
 //go:linkname net_fastrand net.fastrand
 func net_fastrand() uint32 { return fastrand() }
diff --git a/src/runtime/symtab.go b/src/runtime/symtab.go
index 7641c491f10..2de518d2e6a 100644
--- a/src/runtime/symtab.go
+++ b/src/runtime/symtab.go
@@ -921,7 +921,7 @@ func pcvalue(f funcInfo, off uint32, targetpc uintptr, cache *pcvalueCache, stri
 			if cache != nil {
 				x := pcvalueCacheKey(targetpc)
 				e := &cache.entries[x]
-				ci := fastrand() % uint32(len(cache.entries[x]))
+				ci := fastrandn(uint32(len(cache.entries[x])))
 				e[ci] = e[0]
 				e[0] = pcvalueCacheEnt{
 					targetpc: targetpc,
diff --git a/src/sync/pool.go b/src/sync/pool.go
index 1ae70127ac2..9802f29d6f6 100644
--- a/src/sync/pool.go
+++ b/src/sync/pool.go
@@ -71,7 +71,7 @@ type poolLocal struct {
 }
 
 // from runtime
-func fastrand() uint32
+func fastrandn(n uint32) uint32
 
 var poolRaceHash [128]uint64
 
@@ -92,7 +92,7 @@ func (p *Pool) Put(x interface{}) {
 		return
 	}
 	if race.Enabled {
-		if fastrand()%4 == 0 {
+		if fastrandn(4) == 0 {
 			// Randomly drop x on floor.
 			return
 		}