diff --git a/thread_options.h b/thread_options.h
index 2f807cd..79c3a89 100644
--- a/thread_options.h
+++ b/thread_options.h
@@ -100,7 +100,7 @@
 	unsigned int do_disk_util;
 	unsigned int override_sync;
 	unsigned int rand_repeatable;
-	unsigned int rand_seed;
+	unsigned long long rand_seed;
 	unsigned int use_os_rand;
 	unsigned int log_avg_msec;
 	unsigned int norandommap;
@@ -324,7 +324,7 @@
 	uint32_t do_disk_util;
 	uint32_t override_sync;
 	uint32_t rand_repeatable;
-	uint32_t rand_seed;
+	uint64_t rand_seed;
 	uint32_t use_os_rand;
 	uint32_t log_avg_msec;
 	uint32_t norandommap;