diff --git a/protocols/meson.build b/protocols/meson.build
index ab0cfa2..cefdf64 100644
--- a/protocols/meson.build
+++ b/protocols/meson.build
@@ -11,15 +11,12 @@ wayland_scanner_client = generator(
   output: '@BASENAME@-client-protocol.h',
   arguments: ['client-header', '@INPUT@', '@OUTPUT@'])
 
+wayland_xmls = [
+  wl_protocol_dir + '/stable/xdg-shell/xdg-shell.xml',
+  'wlr-layer-shell-unstable-v1.xml',
+  'net-tapesoftware-dwl-wm-unstable-v1.xml',
+]
 wayland_sources = [
-  wayland_scanner_code.process(
-    wl_protocol_dir + '/stable/xdg-shell/xdg-shell.xml',
-    'wlr-layer-shell-unstable-v1.xml',
-    'net-tapesoftware-dwl-wm-unstable-v1.xml'
-    ),
-  wayland_scanner_client.process(
-    wl_protocol_dir + '/stable/xdg-shell/xdg-shell.xml',
-    'wlr-layer-shell-unstable-v1.xml',
-    'net-tapesoftware-dwl-wm-unstable-v1.xml'
-    ),
-  ]
+  wayland_scanner_code.process(wayland_xmls),
+  wayland_scanner_client.process(wayland_xmls),
+]
diff --git a/src/shm_buffer.cpp b/src/shm_buffer.cpp
index fc16265..1dfb167 100644
--- a/src/shm_buffer.cpp
+++ b/src/shm_buffer.cpp
@@ -13,12 +13,13 @@ ShmBuffer::ShmBuffer(int w, int h, wl_shm_format format)
     , height(h)
     , stride(w*4)
 {
-    auto oneSize = stride*h;
-    _totalSize = oneSize * n;
+    auto oneSize = stride*size_t(h);
+    auto totalSize = oneSize * n;
     auto fd = memfd_create("wl_shm", MFD_CLOEXEC);
-    ftruncate(fd, _totalSize);
-    auto pool = wl_shm_create_pool(shm, fd, _totalSize);
-    auto ptr = reinterpret_cast<uint8_t*>(mmap(nullptr, _totalSize, PROT_READ | PROT_WRITE, MAP_SHARED, fd, 0));
+    ftruncate(fd, totalSize);
+    auto pool = wl_shm_create_pool(shm, fd, totalSize);
+    auto ptr = reinterpret_cast<uint8_t*>(mmap(nullptr, totalSize, PROT_READ | PROT_WRITE, MAP_SHARED, fd, 0));
+    _mapping = MemoryMapping {ptr, totalSize};
     close(fd);
     for (auto i=0; i<n; i++) {
         auto offset = oneSize*i;
@@ -30,13 +31,6 @@ ShmBuffer::ShmBuffer(int w, int h, wl_shm_format format)
     wl_shm_pool_destroy(pool);
 }
 
-ShmBuffer::~ShmBuffer()
-{
-    if (_buffers[0].data) {
-        munmap(_buffers[0].data, _totalSize);
-    }
-}
-
-uint8_t* ShmBuffer::data() const { return _buffers[_current].data; }
-wl_buffer* ShmBuffer::buffer() const { return _buffers[_current].buffer.get(); }
+uint8_t* ShmBuffer::data() { return _buffers[_current].data; }
+wl_buffer* ShmBuffer::buffer() { return _buffers[_current].buffer.get(); }
 void ShmBuffer::flip() { _current = 1-_current; }
diff --git a/src/shm_buffer.hpp b/src/shm_buffer.hpp
index 493057b..176f29a 100644
--- a/src/shm_buffer.hpp
+++ b/src/shm_buffer.hpp
@@ -3,9 +3,28 @@
 
 #pragma once
 #include <array>
+#include <sys/mman.h>
 #include <wayland-client.h>
 #include "common.hpp"
 
+class MemoryMapping {
+    void* _ptr {nullptr};
+    size_t _size {0};
+public:
+    MemoryMapping() { }
+    explicit MemoryMapping(void *ptr, size_t size) : _ptr(ptr), _size(size) { }
+    MemoryMapping(const MemoryMapping&) = delete;
+    MemoryMapping(MemoryMapping &&other) { swap(other); }
+    MemoryMapping& operator=(const MemoryMapping &other) = delete;
+    MemoryMapping& operator=(MemoryMapping &&other) { swap(other); return *this; }
+    ~MemoryMapping() { if (_ptr) munmap(_ptr, _size); }
+    void swap(MemoryMapping &other) {
+        using std::swap;
+        swap(_ptr, other._ptr);
+        swap(_size, other._size);
+    }
+};
+
 // double buffered shm
 // format is must be 32-bit
 class ShmBuffer {
@@ -15,18 +34,12 @@ class ShmBuffer {
     };
     std::array<Buf, 2> _buffers;
     int _current {0};
-    size_t _totalSize {0};
+    MemoryMapping _mapping;
 public:
     int width, height, stride;
 
     explicit ShmBuffer(int width, int height, wl_shm_format format);
-    ShmBuffer(const ShmBuffer&) = delete;
-    ShmBuffer(ShmBuffer&&) = default;
-    ShmBuffer& operator=(const ShmBuffer&) = delete;
-    ShmBuffer& operator=(ShmBuffer&&) = default;
-    ~ShmBuffer();
-
-    uint8_t* data() const;
-    wl_buffer* buffer() const;
+    uint8_t* data();
+    wl_buffer* buffer();
     void flip();
 };