diff --git a/src/buffer.h b/src/buffer.h
index 756c5e6b..96bf7cf7 100644
--- a/src/buffer.h
+++ b/src/buffer.h
@@ -43,7 +43,8 @@ template <size_t N> struct Buffer {
   // |src|.  Returns number of bytes written.
   size_t write(const void *src, size_t count) {
     count = std::min(count, wleft());
-    last = std::copy_n(static_cast<const uint8_t *>(src), count, last);
+    auto p = static_cast<const uint8_t *>(src);
+    last = std::copy(p, p + count, last);
     return count;
   }
   size_t write(size_t count) {
diff --git a/src/memchunk.h b/src/memchunk.h
index 64e386af..6df982cd 100644
--- a/src/memchunk.h
+++ b/src/memchunk.h
@@ -134,7 +134,7 @@ template <typename Memchunk> struct Memchunks {
 
     for (;;) {
       auto n = std::min(static_cast<size_t>(last - first), tail->left());
-      tail->last = std::copy_n(first, n, tail->last);
+      tail->last = std::copy(first, first + n, tail->last);
       first += n;
       len += n;
       if (first == last) {
@@ -165,7 +165,7 @@ template <typename Memchunk> struct Memchunks {
       auto n = std::min(static_cast<size_t>(last - first), m->len());
 
       assert(m->len());
-      first = std::copy_n(m->pos, n, first);
+      first = std::copy(m->pos, m->pos + n, first);
       m->pos += n;
       len -= n;
       if (m->len() > 0) {