diff --git a/configure.ac b/configure.ac
index d2d914e4..9d624082 100644
--- a/configure.ac
+++ b/configure.ac
@@ -134,6 +134,8 @@ AC_TYPE_SIZE_T
 AC_TYPE_SSIZE_T
 AC_TYPE_UID_T
 
+AC_CHECK_SIZEOF([off_t])
+
 dnl Checks for required libraries
 
 dnl
diff --git a/src/fserve.c b/src/fserve.c
index 13be4478..e90c644d 100644
--- a/src/fserve.c
+++ b/src/fserve.c
@@ -21,22 +21,27 @@
 #include <sys/types.h>
 #include <sys/stat.h>
 #include <errno.h>
+#include <inttypes.h>
 
 #ifdef HAVE_POLL
 #include <poll.h>
 #endif
 
+#if SIZEOF_OFF_T >= 8
+#define SCN_OFF_T  SCNd64
+#define PRI_OFF_T  PRId64
+#else
+#define SCN_OFF_T  SCNd32
+#define PRI_OFF_T  PRId32
+#endif
+
 #ifndef _WIN32
 #include <unistd.h>
 #include <sys/time.h>
 #include <sys/socket.h>
-#define SCN_OFF_T SCNdMAX
-#define PRI_OFF_T PRIdMAX
 #else
 #include <winsock2.h>
 #include <windows.h>
-#define SCN_OFF_T "ld"
-#define PRI_OFF_T "ld"
 #ifndef S_ISREG
 #define S_ISREG(mode)  ((mode) & _S_IFREG)
 #endif