diff --git a/src/AbstractDiskWriter.cc b/src/AbstractDiskWriter.cc
index 4d62bf97..a6191490 100644
--- a/src/AbstractDiskWriter.cc
+++ b/src/AbstractDiskWriter.cc
@@ -373,6 +373,13 @@ void AbstractDiskWriter::ensureMmapWrite(size_t len, int64_t offset)
         return;
       }
 
+      if (static_cast<uint64_t>(std::numeric_limits<size_t>::max()) < static_cast<uint64_t>(filesize)) {
+        // filesize could overflow in 32bit OS with 64bit off_t type
+        // the filesize will be truncated if provided as a 32bit size_t
+        enableMmap_ = false;
+        return;
+      }
+
       int errNum = 0;
       if (static_cast<int64_t>(len + offset) <= filesize) {
 #ifdef __MINGW32__
@@ -391,10 +398,14 @@ void AbstractDiskWriter::ensureMmapWrite(size_t len, int64_t offset)
           errNum = GetLastError();
         }
 #else  // !__MINGW32__
-        mapaddr_ = reinterpret_cast<unsigned char*>(mmap(
-            nullptr, filesize, PROT_READ | PROT_WRITE, MAP_SHARED, fd_, 0));
-        if (!mapaddr_) {
+        void * pa = mmap(nullptr, filesize, PROT_READ | PROT_WRITE, MAP_SHARED, fd_, 0);
+
+        if (pa == MAP_FAILED) {
           errNum = errno;
+          mapaddr_ = nullptr;
+        }
+        else {
+          mapaddr_ = reinterpret_cast<unsigned char*>(pa);
         }
 #endif // !__MINGW32__
         if (mapaddr_) {