diff --git a/src/memory/map.cpp b/src/memory/map.cpp
index b1e8b646..d421e9c9 100644
--- a/src/memory/map.cpp
+++ b/src/memory/map.cpp
@@ -37,6 +37,10 @@
 #include <bitcoin/database/error.hpp>
 #include <bitcoin/database/file/file.hpp>
 
+#if defined(HAVE_APPLE)
+int fallocate(int fd, int, off_t offset, off_t len) NOEXCEPT;
+#endif
+
 namespace libbitcoin {
 namespace database {
 
@@ -554,47 +558,6 @@ bool map::remap_(size_t size) NOEXCEPT
     return finalize_(size);
 }
 
-#if defined(HAVE_APPLE)
-// ::fallocate is not defined on macOS, so implement. Ignores mode (linux).
-int fallocate(int fd, int, size_t offset, size_t len) NOEXCEPT
-{
-    fstore_t store
-    {
-        // Prefer contiguous allocation
-        .fst_flags = F_ALLOCATECONTIG,
-
-        // Allocate from EOF
-        .fst_posmode = F_PEOFPOSMODE,
-
-        // Start from current capacity
-        .fst_offset = offset,
-
-        // Delta size
-        .fst_length = len,
-
-        // Output: actual bytes allocated
-        .fst_bytesalloc = 0
-    };
-
-    // Try contiguous allocation.
-    auto result = ::fcntl(fd, F_PREALLOCATE, &store);
-
-    // Fallback to non-contiguous.
-    if ((result == fail) && (errno != ENOSPC))
-    {
-        store.fst_flags = F_ALLOCATEALL;
-        result = ::fcntl(fd, F_PREALLOCATE, &store);
-    }
-
-    if (result == fail)
-        return fail;
-
-    // Extend file to new size (required for mmap). This is not required on
-    // Linux because fallocate(2) automatically extends file's logical size.
-    return ::ftruncate(fd, offset + len);
-}
-#endif // HAVE_APPLE
-
 // disk_full: space is set but no code is set with false return.
 bool map::resize_(size_t size) NOEXCEPT
 {
@@ -681,3 +644,46 @@ BC_POP_WARNING()
 
 } // namespace database
 } // namespace libbitcoin
+
+#if defined(HAVE_APPLE)
+// ::fallocate is not defined on macOS, so implement. Ignores mode (linux).
+int fallocate(int fd, int, off_t offset, off_t len) NOEXCEPT
+{
+    constexpr auto fail = -1;
+
+    fstore_t store
+    {
+        // Prefer contiguous allocation
+        .fst_flags = F_ALLOCATECONTIG,
+
+        // Allocate from EOF
+        .fst_posmode = F_PEOFPOSMODE,
+
+        // Start from current capacity
+        .fst_offset = offset,
+
+        // Delta size
+        .fst_length = len,
+
+        // Output: actual bytes allocated
+        .fst_bytesalloc = 0
+    };
+
+    // Try contiguous allocation.
+    auto result = ::fcntl(fd, F_PREALLOCATE, &store);
+
+    // Fallback to non-contiguous.
+    if ((result == fail) && (errno != ENOSPC))
+    {
+        store.fst_flags = F_ALLOCATEALL;
+        result = ::fcntl(fd, F_PREALLOCATE, &store);
+    }
+
+    if (result == fail)
+        return fail;
+
+    // Extend file to new size (required for mmap). This is not required on
+    // Linux because fallocate(2) automatically extends file's logical size.
+    return ::ftruncate(fd, offset + len);
+}
+#endif // HAVE_APPLE