diff --git a/buffer.c b/buffer.c
index 497b8b5a..eb2d84b2 100644
--- a/buffer.c
+++ b/buffer.c
@@ -2642,7 +2642,7 @@ done:
  */
 int
 evbuffer_add_file(struct evbuffer *outbuf, int fd,
-    off_t offset, off_t length)
+    ev_off_t offset, ev_off_t length)
 {
 #if defined(USE_SENDFILE) || defined(_EVENT_HAVE_MMAP)
 	struct evbuffer_chain *chain;
@@ -2738,7 +2738,7 @@ evbuffer_add_file(struct evbuffer *outbuf, int fd,
 			return (-1);
 
 #ifdef WIN32
-#define lseek _lseek
+#define lseek _lseeki64
 #endif
 		if (lseek(fd, offset, SEEK_SET) == -1) {
 			evbuffer_free(tmp);
diff --git a/include/event2/buffer.h b/include/event2/buffer.h
index b5feefae..d6538071 100644
--- a/include/event2/buffer.h
+++ b/include/event2/buffer.h
@@ -375,8 +375,8 @@ int evbuffer_add_reference(struct evbuffer *outbuf,
   @return 0 if successful, or -1 if an error occurred
 */
 
-int evbuffer_add_file(struct evbuffer *output, int fd, off_t offset,
-    off_t length);
+int evbuffer_add_file(struct evbuffer *output, int fd, ev_off_t offset,
+    ev_off_t length);
 
 /**
   Append a formatted string to the end of an evbuffer.
diff --git a/include/event2/util.h b/include/event2/util.h
index 7e21410d..11807784 100644
--- a/include/event2/util.h
+++ b/include/event2/util.h
@@ -161,6 +161,12 @@ extern "C" {
 #define ev_ssize_t ssize_t
 #endif
 
+#ifdef WIN32
+#define ev_off_t ev_int64_t
+#else
+#define ev_off_t off_t
+#endif
+
 /* Limits for integer types.
 
    We're making two assumptions here: