diff --git a/mdadm.h b/mdadm.h
index 1a7db81..2a5e1c8 100644
--- a/mdadm.h
+++ b/mdadm.h
@@ -28,6 +28,7 @@
  */
 
 #define	_GNU_SOURCE
+#define _FILE_OFFSET_BITS 64
 #include	<unistd.h>
 #if !defined(__dietlibc__) && !defined(__KLIBC__)
 extern __off64_t lseek64 __P ((int __fd, __off64_t __offset, int __whence));
diff --git a/util.c b/util.c
index 1ba236b..bd46999 100644
--- a/util.c
+++ b/util.c
@@ -830,6 +830,11 @@ struct supertype *guess_super(int fd)
 int get_dev_size(int fd, char *dname, unsigned long long *sizep)
 {
 	unsigned long long ldsize;
+	struct stat st;
+
+	if (fstat(fd, &st) != -1 && S_ISREG(st.st_mode))
+		ldsize = (unsigned long long)st.st_size;
+	else
 #ifdef BLKGETSIZE64
 	if (ioctl(fd, BLKGETSIZE64, &ldsize) != 0)
 #endif