diff --git a/src/runtime/export_test.go b/src/runtime/export_test.go
index 6335dab41b..fc681b140e 100644
--- a/src/runtime/export_test.go
+++ b/src/runtime/export_test.go
@@ -53,6 +53,9 @@ var CgoCheckPointer = cgoCheckPointer
 const TracebackInnerFrames = tracebackInnerFrames
 const TracebackOuterFrames = tracebackOuterFrames
 
+var MapKeys = keys
+var MapValues = values
+
 var LockPartialOrder = lockPartialOrder
 
 type LockRank lockRank
diff --git a/src/runtime/map.go b/src/runtime/map.go
index 5b264b0713..68ba4e44b8 100644
--- a/src/runtime/map.go
+++ b/src/runtime/map.go
@@ -1651,7 +1651,7 @@ func copyKeys(t *maptype, h *hmap, b *bmap, s *slice, offset uint8) {
 			if s.len >= s.cap {
 				fatal("concurrent map read and map write")
 			}
-			typedmemmove(t.Key, add(s.array, uintptr(s.len)*uintptr(t.KeySize)), k)
+			typedmemmove(t.Key, add(s.array, uintptr(s.len)*uintptr(t.Key.Size())), k)
 			s.len++
 		}
 		b = b.overflow(t)
@@ -1716,7 +1716,7 @@ func copyValues(t *maptype, h *hmap, b *bmap, s *slice, offset uint8) {
 			if s.len >= s.cap {
 				fatal("concurrent map read and map write")
 			}
-			typedmemmove(t.Elem, add(s.array, uintptr(s.len)*uintptr(t.ValueSize)), ele)
+			typedmemmove(t.Elem, add(s.array, uintptr(s.len)*uintptr(t.Elem.Size())), ele)
 			s.len++
 		}
 		b = b.overflow(t)
diff --git a/src/runtime/map_test.go b/src/runtime/map_test.go
index 7e911b9fc9..2c51236f16 100644
--- a/src/runtime/map_test.go
+++ b/src/runtime/map_test.go
@@ -1434,3 +1434,33 @@ func TestLoadFactor(t *testing.T) {
 		}
 	}
 }
+
+func TestMapKeys(t *testing.T) {
+	type key struct {
+		s   string
+		pad [128]byte // sizeof(key) > abi.MapMaxKeyBytes
+	}
+	m := map[key]int{{s: "a"}: 1, {s: "b"}: 2}
+	keys := make([]key, 0, len(m))
+	runtime.MapKeys(m, unsafe.Pointer(&keys))
+	for _, k := range keys {
+		if len(k.s) != 1 {
+			t.Errorf("len(k.s) == %d, want 1", len(k.s))
+		}
+	}
+}
+
+func TestMapValues(t *testing.T) {
+	type val struct {
+		s   string
+		pad [128]byte // sizeof(val) > abi.MapMaxElemBytes
+	}
+	m := map[int]val{1: {s: "a"}, 2: {s: "b"}}
+	vals := make([]val, 0, len(m))
+	runtime.MapValues(m, unsafe.Pointer(&vals))
+	for _, v := range vals {
+		if len(v.s) != 1 {
+			t.Errorf("len(v.s) == %d, want 1", len(v.s))
+		}
+	}
+}