diff --git a/filesetup.c b/filesetup.c
index 84eaed6..aa908ad 100644
--- a/filesetup.c
+++ b/filesetup.c
@@ -752,7 +752,7 @@ uint64_t get_start_offset(struct thread_data *td, struct fio_file *f)
 		return f->real_file_size;
 
 	return td->o.start_offset +
-		(td->thread_number - 1) * td->o.offset_increment;
+		td->subjob_number * td->o.offset_increment;
 }
 
 /*
diff --git a/fio.1 b/fio.1
index 62f40ea..10f4b77 100644
--- a/fio.1
+++ b/fio.1
@@ -658,9 +658,10 @@ Offset in the file to start I/O. Data before the offset will not be touched.
 .BI offset_increment \fR=\fPint
 If this is provided, then the real offset becomes the
 offset + offset_increment * thread_number, where the thread number is a counter
-that starts at 0 and is incremented for each job. This option is useful if
-there are several jobs which are intended to operate on a file in parallel in
-disjoint segments, with even spacing between the starting points.
+that starts at 0 and is incremented for each sub-job (i.e. when numjobs option
+is specified). This option is useful if there are several jobs which are
+intended to operate on a file in parallel in disjoint segments, with even
+spacing between the starting points.
 .TP
 .BI number_ios \fR=\fPint
 Fio will normally perform IOs until it has exhausted the size of the region
diff --git a/fio.h b/fio.h
index 4d4af0a..b0c247e 100644
--- a/fio.h
+++ b/fio.h
@@ -101,6 +101,7 @@ struct thread_data {
 	char verror[FIO_VERROR_SIZE];
 	pthread_t thread;
 	unsigned int thread_number;
+	unsigned int subjob_number;
 	unsigned int groupid;
 	struct thread_stat ts;
 
diff --git a/init.c b/init.c
index a546861..a454e5e 100644
--- a/init.c
+++ b/init.c
@@ -363,6 +363,7 @@ static struct thread_data *get_new_job(int global, struct thread_data *parent,
 	profile_add_hooks(td);
 
 	td->thread_number = thread_number;
+	td->subjob_number = 0;
 
 	if (!parent->o.group_reporting)
 		stat_number++;
@@ -1198,6 +1199,7 @@ static int add_job(struct thread_data *td, const char *jobname, int job_add_num,
 		td_new->o.numjobs = 1;
 		td_new->o.stonewall = 0;
 		td_new->o.new_group = 0;
+		td_new->subjob_number = numjobs;
 
 		if (file_alloced) {
 			if (td_new->files) {