diff --git a/nmap.cc b/nmap.cc
index 5b2fa3ac4..3370a558e 100644
--- a/nmap.cc
+++ b/nmap.cc
@@ -2335,14 +2335,14 @@ int nmap_main(int argc, char *argv[]) {
 
 int gather_logfile_resumption_state(char *fname, int *myargc, char ***myargv) {
   char *filestr;
-  int filelen;
+  s64 filelen;
   char nmap_arg_buffer[4096]; /* roughly aligned with arg_parse limit */
   struct in_addr lastip;
   char *p, *q, *found, *lastipstr; /* I love C! */
   /* We mmap it read/write since we will change the last char to a newline if it is not already */
   filestr = mmapfile(fname, &filelen, O_RDWR);
   if (!filestr) {
-    fatal("Could not mmap() %s file. Make sure you have enough rights and the file really exists.", fname);
+    pfatal("Could not mmap() %s file", fname);
   }
 
   if (filelen < 20) {
@@ -2486,7 +2486,7 @@ int gather_logfile_resumption_state(char *fname, int *myargc, char ***myargv) {
   /* Ensure the log file ends with a newline */
   filestr[filelen - 1] = '\n';
   if (munmap(filestr, filelen) != 0)
-    gh_perror("%s: error in munmap(%p, %u)", __func__, filestr, filelen);
+    gh_perror("%s: error in munmap(%p, %ld)", __func__, filestr, filelen);
 
   return 0;
 }
diff --git a/utils.cc b/utils.cc
index 84418c905..e079807c0 100644
--- a/utils.cc
+++ b/utils.cc
@@ -605,7 +605,7 @@ static int open2mmap_flags(int open_flags)
    undefined, and errno is set to something appropriate. The user is responsible
    for doing an munmap(ptr, length) when finished with it. openflags should be
    O_RDONLY or O_RDWR, or O_WRONLY. */
-char *mmapfile(char *fname, int *length, int openflags) {
+char *mmapfile(char *fname, s64 *length, int openflags) {
   struct stat st;
   int fd;
   int mmap_flags;
@@ -654,9 +654,10 @@ char *mmapfile(char *fname, int *length, int openflags) {
 
 static HANDLE gmap = NULL;
 
-char *mmapfile(char *fname, int *length, int openflags) {
+char *mmapfile(char *fname, s64 *length, int openflags) {
   HANDLE fd;
   DWORD mflags, oflags;
+  DWORD lowsize, highsize;
   char *fileptr;
 
   if (!length || !fname) {
@@ -683,11 +684,18 @@ char *mmapfile(char *fname, int *length, int openflags) {
   if (!fd)
     pfatal ("%s(%u): CreateFile()", __FILE__, __LINE__);
 
-  *length = (int) GetFileSize (fd, NULL);
+  lowsize = GetFileSize (fd, &highsize);
+  if (lowsize == INVALID_FILE_SIZE && GetLastError() != NO_ERROR) {
+    pfatal("%s(%u): GetFileSize(), file '%s'", __FILE__, __LINE__, fname);
+  }
+  *length = lowsize + highsize << sizeof(DWORD);
+  if (*length < 0) {
+    fatal("%s(%u): size too large, file '%s'", __FILE__, __LINE__, fname);
+  }
 
   gmap = CreateFileMapping (fd, NULL, mflags, 0, 0, NULL);
   if (!gmap) {
-    pfatal("%s(%u): CreateFileMapping(), file '%s', length %d, mflags %08lX",
+    pfatal("%s(%u): CreateFileMapping(), file '%s', length %I64d, mflags %08lX",
            __FILE__, __LINE__, fname, *length, mflags);
   }
 
@@ -696,7 +704,7 @@ char *mmapfile(char *fname, int *length, int openflags) {
     pfatal ("%s(%u): MapViewOfFile()", __FILE__, __LINE__);
 
   if (o.debugging > 2) {
-    log_write(LOG_PLAIN, "%s(): fd %08lX, gmap %08lX, fileptr %08lX, length %d\n",
+    log_write(LOG_PLAIN, "%s(): fd %08lX, gmap %08lX, fileptr %08lX, length %I64d\n",
               __func__, (DWORD)fd, (DWORD)gmap, (DWORD)fileptr, *length);
   }
 
diff --git a/utils.h b/utils.h
index 54be535ce..7c88c3e33 100644
--- a/utils.h
+++ b/utils.h
@@ -189,7 +189,7 @@ u8 *parse_hex_string(char *str, size_t *outlen);
 
 int cpe_get_part(const char *cpe);
 
-char *mmapfile(char *fname, int *length, int openflags);
+char *mmapfile(char *fname, s64 *length, int openflags);
 
 #ifdef WIN32
 int win32_munmap(char *filestr, int filelen);