diff --git a/util/env_posix.cc b/util/env_posix.cc
index cb1f6fc0..56b773e2 100644
--- a/util/env_posix.cc
+++ b/util/env_posix.cc
@@ -101,7 +101,7 @@ class PosixMmapReadableFile: public RandomAccessFile {
   // base[0,length-1] contains the mmapped contents of the file.
   PosixMmapReadableFile(const std::string& fname, void* base, size_t length)
       : filename_(fname), mmapped_region_(base), length_(length) { }
-  virtual ~PosixMmapReadableFile() { munmap(mmapped_region_, length_); }
+  virtual ~PosixMmapReadableFile() { munmap((char *)mmapped_region_, length_); }
 
   virtual Status Read(uint64_t offset, size_t n, Slice* result,
                       char* scratch) const {