diff --git a/src/common/mm_io.cpp b/src/common/mm_io.cpp
index 35e1b4c11..454f55d29 100644
--- a/src/common/mm_io.cpp
+++ b/src/common/mm_io.cpp
@@ -69,11 +69,13 @@ mm_io_c::mm_io_c(const char *path,
     throw exception();
 
   file_name = safestrdup(path);
+  dos_style_newlines = false;
 }
 
 mm_io_c::mm_io_c() {
   file_name = NULL;
   file = NULL;
+  dos_style_newlines = false;
 }
 
 mm_io_c::~mm_io_c() {
@@ -175,11 +177,13 @@ mm_io_c::mm_io_c(const char *path,
     throw exception();
 
   file_name = safestrdup(path);
+  dos_style_newlines = true;
 }
 
 mm_io_c::mm_io_c() {
   file_name = NULL;
   file = NULL;
+  dos_style_newlines = true;
 }
 
 mm_io_c::~mm_io_c() {
@@ -543,9 +547,9 @@ int
 mm_io_c::printf(const char *fmt,
                 ...) {
   va_list ap;
-  string new_fmt;
+  string new_fmt, s;
   char *new_string;
-  int len;
+  int len, pos;
 
   fix_format(fmt, new_fmt);
   va_start(ap, fmt);
@@ -553,10 +557,17 @@ mm_io_c::printf(const char *fmt,
   new_string = (char *)safemalloc(len + 1);
   vsprintf(new_string, new_fmt.c_str(), ap);
   va_end(ap);
-  len = write(new_string, len);
+  s = new_string;
   safefree(new_string);
+  if (dos_style_newlines) {
+    pos = 0;
+    while ((pos = s.find('\n', pos)) >= 0) {
+      s.replace(pos, 1, "\n\r");
+      pos += 2;
+    }
+  }
 
-  return len;
+  return write(s.c_str(), s.length());
 }
 
 /*
diff --git a/src/common/mm_io.h b/src/common/mm_io.h
index 48379d526..c68ef641d 100644
--- a/src/common/mm_io.h
+++ b/src/common/mm_io.h
@@ -39,6 +39,7 @@ protected:
   char *file_name;
   void *file;
   stack<int64_t> positions;
+  bool dos_style_newlines;
 
 public:
   mm_io_c();
@@ -78,6 +79,9 @@ public:
   virtual int truncate(int64_t pos);
 
   virtual int printf(const char *fmt, ...);
+  virtual void use_dos_style_newlines(bool yes) {
+    dos_style_newlines = yes;
+  }
 };
 
 class MTX_DLL_API mm_null_io_c: public mm_io_c {