diff --git a/include-fd/stdplus/fd/gmock.hpp b/include-fd/stdplus/fd/gmock.hpp
index 08c66fb..4ec3de0 100644
--- a/include-fd/stdplus/fd/gmock.hpp
+++ b/include-fd/stdplus/fd/gmock.hpp
@@ -48,8 +48,8 @@
     MOCK_METHOD(void, fcntlSetfl, (FileFlags flags), (override));
     MOCK_METHOD(FileFlags, fcntlGetfl, (), (const, override));
     MOCK_METHOD(std::span<std::byte>, mmap,
-                (std::span<std::byte> window, ProtFlags prot, MMapFlags flags,
-                 off_t offset),
+                (std::byte * window, std::size_t size, ProtFlags prot,
+                 MMapFlags flags, off_t offset),
                 (override));
     MOCK_METHOD(void, munmap, (std::span<std::byte> window), (override));
 };
diff --git a/include-fd/stdplus/fd/impl.hpp b/include-fd/stdplus/fd/impl.hpp
index fe3af81..e3991dc 100644
--- a/include-fd/stdplus/fd/impl.hpp
+++ b/include-fd/stdplus/fd/impl.hpp
@@ -40,8 +40,9 @@
     FileFlags fcntlGetfl() const override;
 
   protected:
-    std::span<std::byte> mmap(std::span<std::byte> window, ProtFlags prot,
-                              MMapFlags flags, off_t offset) override;
+    std::span<std::byte> mmap(std::byte* window, std::size_t size,
+                              ProtFlags prot, MMapFlags flags,
+                              off_t offset) override;
     void munmap(std::span<std::byte> window) override;
 };
 
diff --git a/include-fd/stdplus/fd/intf.hpp b/include-fd/stdplus/fd/intf.hpp
index 70ff828..b15cda6 100644
--- a/include-fd/stdplus/fd/intf.hpp
+++ b/include-fd/stdplus/fd/intf.hpp
@@ -149,8 +149,8 @@
 
   protected:
     virtual std::span<std::byte>
-        mmap(std::span<std::byte> window, ProtFlags prot, MMapFlags flags,
-             off_t offset) = 0;
+        mmap(std::byte* window, std::size_t size, ProtFlags prot,
+             MMapFlags flags, off_t offset) = 0;
     virtual void munmap(std::span<std::byte> window) = 0;
     friend class MMap;
 };
diff --git a/include-fd/stdplus/fd/mmap.hpp b/include-fd/stdplus/fd/mmap.hpp
index f41f562..0bc1f81 100644
--- a/include-fd/stdplus/fd/mmap.hpp
+++ b/include-fd/stdplus/fd/mmap.hpp
@@ -14,13 +14,8 @@
 class MMap
 {
   public:
-    inline MMap(Fd& fd, size_t window_size, ProtFlags prot, MMapFlags flags,
-                off_t offset) :
-        MMap(fd,
-             std::span<std::byte>{static_cast<std::byte*>(nullptr),
-                                  window_size},
-             prot, flags, offset)
-    {}
+    MMap(Fd& fd, size_t window_size, ProtFlags prot, MMapFlags flags,
+         off_t offset);
     MMap(Fd& fd, std::span<std::byte> window, ProtFlags prot, MMapFlags flags,
          off_t offset);
 
diff --git a/src/fd/impl.cpp b/src/fd/impl.cpp
index 3147e64..5f9fe7f 100644
--- a/src/fd/impl.cpp
+++ b/src/fd/impl.cpp
@@ -188,16 +188,16 @@
     return FileFlags(CHECK_ERRNO(::fcntl(get(), F_GETFL), "fcntl getfl"));
 }
 
-std::span<std::byte> FdImpl::mmap(std::span<std::byte> window, ProtFlags prot,
-                                  MMapFlags flags, off_t offset)
+std::span<std::byte> FdImpl::mmap(std::byte* window, std::size_t size,
+                                  ProtFlags prot, MMapFlags flags, off_t offset)
 {
-    auto ret = ::mmap(window.data(), window.size(), static_cast<int>(prot),
+    auto ret = ::mmap(window, size, static_cast<int>(prot),
                       static_cast<int>(flags), get(), offset);
     if (ret == MAP_FAILED)
     {
         util::doError(errno, "mmap");
     }
-    return {reinterpret_cast<std::byte*>(ret), window.size()};
+    return {reinterpret_cast<std::byte*>(ret), size};
 }
 
 void FdImpl::munmap(std::span<std::byte> window)
diff --git a/src/fd/mmap.cpp b/src/fd/mmap.cpp
index 7026aa6..4718121 100644
--- a/src/fd/mmap.cpp
+++ b/src/fd/mmap.cpp
@@ -6,8 +6,13 @@
 namespace fd
 {
 
+MMap::MMap(Fd& fd, size_t window_size, ProtFlags prot, MMapFlags flags,
+           off_t offset) :
+    mapping(fd.mmap(nullptr, window_size, prot, flags, offset), fd)
+{}
 MMap::MMap(Fd& fd, std::span<std::byte> window, ProtFlags prot, MMapFlags flags,
-           off_t offset) : mapping(fd.mmap(window, prot, flags, offset), fd)
+           off_t offset) :
+    mapping(fd.mmap(window.data(), window.size(), prot, flags, offset), fd)
 {}
 
 std::span<std::byte> MMap::get() const
diff --git a/test/pinned.cpp b/test/pinned.cpp
index 88c9bef..fc907fb 100644
--- a/test/pinned.cpp
+++ b/test/pinned.cpp
@@ -81,6 +81,7 @@
 TEST(PinnedRef, Fundamental)
 {
     Pinned<int> pi = 4;
+    // NOLINTNEXTLINE(clang-analyzer-core.UndefinedBinaryOperatorResult)
     EXPECT_EQ(4, PinnedRef<int>(pi));
     EXPECT_EQ(4, PinnedRef<const int>(pi));
     EXPECT_EQ(4, PinnedRef(pi));