diff --git a/src/runtime/mfixalloc.go b/src/runtime/mfixalloc.go
index a81139a389c..b701a09b40a 100644
--- a/src/runtime/mfixalloc.go
+++ b/src/runtime/mfixalloc.go
@@ -30,7 +30,8 @@ type fixalloc struct {
 	arg    unsafe.Pointer
 	list   *mlink
 	chunk  uintptr // use uintptr instead of unsafe.Pointer to avoid write barriers
-	nchunk uint32
+	nchunk uint32  // bytes remaining in current chunk
+	nalloc uint32  // size of new chunks in bytes
 	inuse  uintptr // in-use bytes now
 	stat   *sysMemStat
 	zero   bool // zero allocations
@@ -63,6 +64,7 @@ func (f *fixalloc) init(size uintptr, first func(arg, p unsafe.Pointer), arg uns
 	f.list = nil
 	f.chunk = 0
 	f.nchunk = 0
+	f.nalloc = uint32(_FixAllocChunk / size * size) // Round _FixAllocChunk down to an exact multiple of size to eliminate tail waste
 	f.inuse = 0
 	f.stat = stat
 	f.zero = true
@@ -84,8 +86,8 @@ func (f *fixalloc) alloc() unsafe.Pointer {
 		return v
 	}
 	if uintptr(f.nchunk) < f.size {
-		f.chunk = uintptr(persistentalloc(_FixAllocChunk, 0, f.stat))
-		f.nchunk = _FixAllocChunk
+		f.chunk = uintptr(persistentalloc(uintptr(f.nalloc), 0, f.stat))
+		f.nchunk = f.nalloc
 	}
 
 	v := unsafe.Pointer(f.chunk)