diff --git a/backend.c b/backend.c
index 6dd078c45e..41f506fcd4 100644
--- a/backend.c
+++ b/backend.c
@@ -1467,7 +1467,10 @@ int init_io_u_buffers(struct thread_data *td)
 	char *p;
 
 	max_units = td->o.iodepth;
-	max_bs = td_max_bs(td);
+	if (td->trim_verify && td->o.trim_zero)
+		max_bs = td_max_bs(td);
+	else
+		max_bs = td_max_rw_bs(td);
 	min_write = td->o.min_bs[DDIR_WRITE];
 	td->orig_buffer_size = (unsigned long long) max_bs
 					* (unsigned long long) max_units;
diff --git a/fio.h b/fio.h
index 8708f04880..227414534b 100644
--- a/fio.h
+++ b/fio.h
@@ -861,6 +861,14 @@ static inline bool should_check_rate(struct thread_data *td)
 	return (td->flags & TD_F_CHECK_RATE) != 0;
 }
 
+/*
+ * This function considers only read and write block sizes.
+ */
+static inline unsigned long long td_max_rw_bs(struct thread_data *td)
+{
+	return max(td->o.max_bs[DDIR_READ], td->o.max_bs[DDIR_WRITE]);
+}
+
 static inline unsigned long long td_max_bs(struct thread_data *td)
 {
 	unsigned long long max_bs;