diff --git a/src/cmd/compile/internal/gc/obj.go b/src/cmd/compile/internal/gc/obj.go
index 3610f16c747..cb9ea52b62c 100644
--- a/src/cmd/compile/internal/gc/obj.go
+++ b/src/cmd/compile/internal/gc/obj.go
@@ -272,14 +272,10 @@ func duintptr(s *Sym, off int, v uint64) int {
 }
 
 func dbvec(s *Sym, off int, bv bvec) int {
-	for j := 0; int32(j) < bv.n; j += 32 {
+	// Runtime reads the bitmaps as byte arrays. Oblige.
+	for j := 0; int32(j) < bv.n; j += 8 {
 		word := bv.b[j/32]
-
-		// Runtime reads the bitmaps as byte arrays. Oblige.
-		off = duint8(s, off, uint8(word))
-		off = duint8(s, off, uint8(word>>8))
-		off = duint8(s, off, uint8(word>>16))
-		off = duint8(s, off, uint8(word>>24))
+		off = duint8(s, off, uint8(word>>(uint(j)%32)))
 	}
 	return off
 }
diff --git a/src/runtime/symtab.go b/src/runtime/symtab.go
index c1cca7037d7..24d63b70c00 100644
--- a/src/runtime/symtab.go
+++ b/src/runtime/symtab.go
@@ -603,5 +603,5 @@ func stackmapdata(stkmap *stackmap, n int32) bitvector {
 	if n < 0 || n >= stkmap.n {
 		throw("stackmapdata: index out of range")
 	}
-	return bitvector{stkmap.nbit, (*byte)(add(unsafe.Pointer(&stkmap.bytedata), uintptr(n*((stkmap.nbit+31)/32*4))))}
+	return bitvector{stkmap.nbit, (*byte)(add(unsafe.Pointer(&stkmap.bytedata), uintptr(n*((stkmap.nbit+7)/8))))}
 }