diff --git a/src/common/buffer.cc b/src/common/buffer.cc
index 03a8b2fa117..e28bcf9bf36 100644
--- a/src/common/buffer.cc
+++ b/src/common/buffer.cc
@@ -28,7 +28,7 @@ atomic_t buffer_total_alloc;
 
 void buffer::list::encode_base64(buffer::list& o)
 {
-  bufferptr bp(length() * 4 / 3 + 1);
+  bufferptr bp(length() * 4 / 3 + 3);
   int l = ceph_armor(bp.c_str(), c_str(), c_str() + length());
   bp.set_length(l);
   o.push_back(bp);
@@ -36,7 +36,7 @@ void buffer::list::encode_base64(buffer::list& o)
 
 void buffer::list::decode_base64(buffer::list& e)
 {
-  bufferptr bp(e.length() * 3 / 4 + 1);
+  bufferptr bp(e.length() * 3 / 4 + 4);
   int l = ceph_unarmor(bp.c_str(), e.c_str(), e.c_str() + e.length());
   assert(l <= (int)bp.length());
   bp.set_length(l);