diff --git a/include/dwarfs/byte_buffer.h b/include/dwarfs/byte_buffer.h
index e335e314..7ce20fc4 100644
--- a/include/dwarfs/byte_buffer.h
+++ b/include/dwarfs/byte_buffer.h
@@ -78,6 +78,8 @@ class mutable_byte_buffer_interface : public byte_buffer_interface {
   // that would reallocate the buffer will throw.
   virtual void freeze_location() = 0;
 
+  virtual void append(void const* data, size_t size) = 0;
+
   virtual internal::malloc_buffer& raw_buffer() = 0;
 };
 
@@ -168,6 +170,13 @@ class mutable_byte_buffer {
 
   void freeze_location() { bb_->freeze_location(); }
 
+  void append(void const* data, size_t size) { bb_->append(data, size); }
+
+  template <detail::byte_range T>
+  void append(T const& data) {
+    append(data.data(), data.size());
+  }
+
   internal::malloc_buffer& raw_buffer() { return bb_->raw_buffer(); }
 
   void swap(mutable_byte_buffer& other) noexcept { std::swap(bb_, other.bb_); }
diff --git a/src/malloc_byte_buffer.cpp b/src/malloc_byte_buffer.cpp
index 76eb3862..55d4ab3a 100644
--- a/src/malloc_byte_buffer.cpp
+++ b/src/malloc_byte_buffer.cpp
@@ -94,6 +94,13 @@ class malloc_byte_buffer_impl : public mutable_byte_buffer_interface {
     frozen_.store(true, std::memory_order_release);
   }
 
+  void append(void const* data, size_t size) override {
+    if (frozen() && data_.size() + size > data_.capacity()) {
+      frozen_error("append beyond capacity");
+    }
+    data_.append(data, size);
+  }
+
   internal::malloc_buffer& raw_buffer() override { return data_; }
 
  private:
diff --git a/src/reader/block_cache_byte_buffer_factory.cpp b/src/reader/block_cache_byte_buffer_factory.cpp
index 53f5d7a0..bd498d94 100644
--- a/src/reader/block_cache_byte_buffer_factory.cpp
+++ b/src/reader/block_cache_byte_buffer_factory.cpp
@@ -27,6 +27,7 @@
  */
 
 #include <cassert>
+#include <cstring>
 #include <stdexcept>
 #include <system_error>
 
@@ -138,6 +139,14 @@ class mmap_byte_buffer_impl : public mutable_byte_buffer_interface {
     // always frozen
   }
 
+  void append(void const* data, size_t size) override {
+    if (size_ + size > data_.size()) {
+      frozen_error("append beyond capacity");
+    }
+    std::memcpy(data_.data() + size_, data, size);
+    size_ += size;
+  }
+
   internal::malloc_buffer& raw_buffer() override {
     throw std::runtime_error(
         "operation not allowed on mmap buffer: raw_buffer");