diff --git a/main.c b/main.c
index c0e811d..1a9efd8 100644
--- a/main.c
+++ b/main.c
@@ -6,7 +6,7 @@
 #include "mmpriv.h"
 #include "getopt.h"
 
-#define MM_VERSION "2.3-r538-dirty"
+#define MM_VERSION "2.3-r539-dirty"
 
 #ifdef __linux__
 #include <sys/resource.h>
diff --git a/map.c b/map.c
index f99626d..e78975e 100644
--- a/map.c
+++ b/map.c
@@ -105,7 +105,7 @@ int mm_set_opt(const char *preset, mm_idxopt_t *io, mm_mapopt_t *mo)
 		mo->mini_batch_size = 50000000;
 	} else if (strcmp(preset, "splice") == 0 || strcmp(preset, "cdna") == 0) {
 		io->is_hpc = 0, io->k = 15, io->w = 5;
-		mo->flag |= MM_F_SPLICE | MM_F_SPLICE_FOR | MM_F_SPLICE_REV;
+		mo->flag |= MM_F_SPLICE | MM_F_SPLICE_FOR | MM_F_SPLICE_REV | MM_F_SPLICE_FLANK;
 		mo->max_gap = 2000, mo->max_gap_ref = mo->bw = 200000;
 		mo->a = 1, mo->b = 2, mo->q = 2, mo->e = 1, mo->q2 = 32, mo->e2 = 0;
 		mo->noncan = 9;
diff --git a/minimap2.1 b/minimap2.1
index b7d7177..97e1790 100644
--- a/minimap2.1
+++ b/minimap2.1
@@ -220,7 +220,9 @@ costs
 In the splice mode, the second gap penalties are not used.
 .TP
 .BI -C \ INT
-Cost for a non-canonical GT-AG splicing [0]
+Cost for a non-canonical GT-AG splicing (effective with
+.BR --splice )
+[0]
 .TP
 .BI -z \ INT
 Break an alignment if the running score drops too quickly along the diagonal of
@@ -243,7 +245,25 @@ both strands;
 no attempt to match GT-AG [n]
 .TP
 .BI --end-bonus \ INT
-Score bonus when alignment extends to the end of the query sequence [10].
+Score bonus when alignment extends to the end of the query sequence [0].
+.TP
+.BR --splice-flank [= yes | no ]
+Assume the next base to a
+.B GT
+donor site tends to be A/G (91% in human and 92% in mouse) and the preceding
+base to a
+.B AG
+acceptor tends to be C/T [yes with
+.BR --splice ].
+This trend is evolutionarily conservative, all the way to S. cerevisiae
+(PMID:18688272). Specifying this option generally leads to higher junction
+accuracy by several percents, so it is applied by default with
+.BR --splice .
+However, the SIRV control does not honor this trend
+(only ~60%). This option reduces accuracy. If you are benchmarking minimap2
+on SIRV data, please add
+.B --splice-flank=no
+to the command line.
 .SS Input/output options
 .TP 10
 .B -a
@@ -261,7 +281,7 @@ the real CIGAR in memory.
 .TP
 .BI -R \ STR
 SAM read group line in a format like
-.RB @RG\\\\tID:foo\\\\tSM:bar
+.B @RG\\\\tID:foo\\\\tSM:bar
 [].
 .TP
 .B -c
@@ -371,8 +391,8 @@ is that this preset is not using HPC minimizers.
 .B splice
 Long-read spliced alignment
 .RB ( -k15
-.B -w5 --splice -g2000 -G200k -A1 -B2 -O2,32 -E1,0 -C9 -z200
-.BR -ub ).
+.B -w5 --splice -g2000 -G200k -A1 -B2 -O2,32 -E1,0 -C9 -z200 -ub
+.BR --splice-flank=yes ).
 In the splice mode, 1) long deletions are taken as introns and represented as
 the
 .RB ` N '