diff --git a/src/runtime/mheap.go b/src/runtime/mheap.go
index 610011863b..cd4634448c 100644
--- a/src/runtime/mheap.go
+++ b/src/runtime/mheap.go
@@ -100,13 +100,11 @@ type mheap struct {
 	// accounting for current progress. If we could only adjust
 	// the slope, it would create a discontinuity in debt if any
 	// progress has already been made.
-	pagesInUse         atomic.Uint64 // pages of spans in stats mSpanInUse
-	pagesSwept         atomic.Uint64 // pages swept this cycle
-	pagesSweptBasis    atomic.Uint64 // pagesSwept to use as the origin of the sweep ratio
-	sweepHeapLiveBasis uint64        // value of gcController.heapLive to use as the origin of sweep ratio; written with lock, read without
-	sweepPagesPerByte  float64       // proportional sweep ratio; written with lock, read without
-	// TODO(austin): pagesInUse should be a uintptr, but the 386
-	// compiler can't 8-byte align fields.
+	pagesInUse         atomic.Uintptr // pages of spans in stats mSpanInUse
+	pagesSwept         atomic.Uint64  // pages swept this cycle
+	pagesSweptBasis    atomic.Uint64  // pagesSwept to use as the origin of the sweep ratio
+	sweepHeapLiveBasis uint64         // value of gcController.heapLive to use as the origin of sweep ratio; written with lock, read without
+	sweepPagesPerByte  float64        // proportional sweep ratio; written with lock, read without
 
 	// Page reclaimer state
 
@@ -1379,7 +1377,7 @@ HaveSpan:
 		atomic.Or8(&arena.pageInUse[pageIdx], pageMask)
 
 		// Update related page sweeper stats.
-		h.pagesInUse.Add(int64(npages))
+		h.pagesInUse.Add(npages)
 	}
 
 	// Make sure the newly allocated span will be observed
@@ -1529,7 +1527,7 @@ func (h *mheap) freeSpanLocked(s *mspan, typ spanAllocType) {
 			print("mheap.freeSpanLocked - span ", s, " ptr ", hex(s.base()), " allocCount ", s.allocCount, " sweepgen ", s.sweepgen, "/", h.sweepgen, "\n")
 			throw("mheap.freeSpanLocked - invalid free")
 		}
-		h.pagesInUse.Add(-int64(s.npages))
+		h.pagesInUse.Add(-s.npages)
 
 		// Clear in-use bit in arena page bitmap.
 		arena, pageIdx, pageMask := pageIndexOf(s.base())