diff --git a/manifest b/manifest
index 58ec6b9026..0d6ebb2ca6 100644
--- a/manifest
+++ b/manifest
@@ -1,5 +1,5 @@
-C Add\sexperimental\sfeature\sto\sdetect\sthreading\sbugs\sin\sapps\sthat\suse\nSQLITE_CONFIG_MULTITHREADED.\sEnabled\sat\scompile\stime\susing\nSQLITE_ENABLE_MULTITHREADED_CHECKS.
-D 2017-11-28T07:52:00.416
+C Lock\sthe\swal\sfile\sfor\sall\ssnapshot\stransactions,\seven\sif\sthey\swould\snot\notherwise\srequire\sthis,\spreventing\scheckpointers\sand\swriters\sfrom\swrapping\sthe\nwal\sfile.\sThis\smeans\sthat\sif\sone\sconnection\shas\san\sopen\ssnapshot\stransaction\nit\sis\sguaranteed\sthat\sa\ssecond\sconnection\scan\sopen\sa\stransaction\son\sthe\ssame\nsnapshot.
+D 2017-11-28T13:39:41.135
 F Makefile.in 6a879cbf01e37f9eac131414955f71774b566502d9a57ded1b8585b507503cb8
 F Makefile.linux-gcc 7bc79876b875010e8c8f9502eb935ca92aa3c434
 F Makefile.msc e5d7606238f55816da99f719969598df5b091aa2e9a6935c9412fcae8f53fc44
@@ -551,7 +551,7 @@ F src/vdbesort.c 731a09e5cb9e96b70c394c1b7cf3860fbe84acca7682e178615eb941a3a0ef2
 F src/vdbetrace.c 48e11ebe040c6b41d146abed2602e3d00d621d7ebe4eb29b0a0f1617fd3c2f6c
 F src/vtab.c 0e4885495172e1bdf54b12cce23b395ac74ef5729031f15e1bc1e3e6b360ed1a
 F src/vxworks.h d2988f4e5a61a4dfe82c6524dd3d6e4f2ce3cdb9
-F src/wal.c beeb71e4eab65dbf0d95f2717efc6ca3c0f5b3090ce67f3de63828f39a6ff053
+F src/wal.c 5a3f464edd64596f601683ed321d12e6fd93c5fb9afdfb3653d6ffd0fee9c48f
 F src/wal.h 8de5d2d3de0956d6f6cb48c83a4012d5f227b8fe940f3a349a4b7e85ebcb492a
 F src/walker.c da987a20d40145c0a03c07d8fefcb2ed363becc7680d0500d9c79915591f5b1f
 F src/where.c 9752b68e03e2044f0faa4708fabb0189769067b660bffa931e1fd65736269659
@@ -1223,6 +1223,7 @@ F test/skipscan5.test 67817a4b6857c47e0e33ba3e506da6f23ef68de2
 F test/skipscan6.test 5866039d03a56f5bd0b3d172a012074a1d90a15b
 F test/snapshot.test 85735bd997a4f6d710140c28fd860519a299649f
 F test/snapshot2.test 925e42427e923262db63c9d7155183f889e3e99feaedec4075f659e51608344f
+F test/snapshot3.test 9719443594a04778861bd20d12596c5f880af177d6cd62f111da3198cafc6096
 F test/snapshot_fault.test 52c5e97ebd218846a8ae2da4d147d3e77d71f963
 F test/soak.test 0b5b6375c9f4110c828070b826b3b4b0bb65cd5f
 F test/softheap1.test 843cd84db9891b2d01b9ab64cef3e9020f98d087
@@ -1678,8 +1679,8 @@ F vsixtest/vsixtest.tcl 6a9a6ab600c25a91a7acc6293828957a386a8a93
 F vsixtest/vsixtest.vcxproj.data 2ed517e100c66dc455b492e1a33350c1b20fbcdc
 F vsixtest/vsixtest.vcxproj.filters 37e51ffedcdb064aad6ff33b6148725226cd608e
 F vsixtest/vsixtest_TemporaryKey.pfx e5b1b036facdb453873e7084e1cae9102ccc67a0
-P e6b89304695be371978e65dddd710c8bd563c66b9c94d23165142b6c235c82e1 12a23c0a66fac5c9674120b390f6abaeaba3f7ff04693b281af1eefb93d6f47c
-R dd8aff31239aebcaa5e5379a4673912d
-T +closed 12a23c0a66fac5c9674120b390f6abaeaba3f7ff04693b281af1eefb93d6f47c
+P 40b598c8392f030f6ed8c63ce81cb0426bb3984397c19c756215f6a569a40164 d71eeaab9ecdeed772047498b781be1f0be0655af284b94cf676bb408ceea8b1
+R e37ca38ceb47340e2d23476ad044f736
+T +closed d71eeaab9ecdeed772047498b781be1f0be0655af284b94cf676bb408ceea8b1
 U dan
-Z bdded6a608898929c58df7d45769809f
+Z a9d291c094a58941f666434dce6709fb
diff --git a/manifest.uuid b/manifest.uuid
index 2cef934b2b..1c080520c0 100644
--- a/manifest.uuid
+++ b/manifest.uuid
@@ -1 +1 @@
-40b598c8392f030f6ed8c63ce81cb0426bb3984397c19c756215f6a569a40164
\ No newline at end of file
+b81a31495bd27c1d96f7df653da3502054240cb5acf66b860da7f0f9b422a524
\ No newline at end of file
diff --git a/src/wal.c b/src/wal.c
index 376151e1a8..7b49f3dab4 100644
--- a/src/wal.c
+++ b/src/wal.c
@@ -2494,8 +2494,7 @@ static int walTryBeginRead(Wal *pWal, int *pChanged, int useWal, int cnt){
   pInfo = walCkptInfo(pWal);
   if( !useWal && pInfo->nBackfill==pWal->hdr.mxFrame
 #ifdef SQLITE_ENABLE_SNAPSHOT
-   && (pWal->pSnapshot==0 || pWal->hdr.mxFrame==0
-     || 0==memcmp(&pWal->hdr, pWal->pSnapshot, sizeof(WalIndexHdr)))
+   && (pWal->pSnapshot==0 || pWal->hdr.mxFrame==0)
 #endif
   ){
     /* The WAL has been completely backfilled (or it is empty).
diff --git a/test/snapshot3.test b/test/snapshot3.test
new file mode 100644
index 0000000000..266f43dfd4
--- /dev/null
+++ b/test/snapshot3.test
@@ -0,0 +1,100 @@
+# 2016 September 23
+#
+# The author disclaims copyright to this source code.  In place of
+# a legal notice, here is a blessing:
+#
+#    May you do good and not evil.
+#    May you find forgiveness for yourself and forgive others.
+#    May you share freely, never taking more than you give.
+#
+#***********************************************************************
+# This file implements regression tests for SQLite library. The focus
+# of this file is the sqlite3_snapshot_xxx() APIs.
+#
+
+set testdir [file dirname $argv0]
+source $testdir/tester.tcl
+ifcapable !snapshot {finish_test; return}
+set testprefix snapshot3
+
+# This test does not work with the inmemory_journal permutation. The reason
+# is that each connection opened as part of this permutation executes
+# "PRAGMA journal_mode=memory", which fails if the database is in wal mode
+# and there are one or more existing connections.
+if {[permutation]=="inmemory_journal"} {
+  finish_test
+  return
+}
+
+#-------------------------------------------------------------------------
+# This block of tests verifies that it is not possible to wrap the wal
+# file - using a writer or a "PRAGMA wal_checkpoint = TRUNCATE" - while
+# there is an open snapshot transaction (transaction opened using
+# sqlite3_snapshot_open()).
+#
+do_execsql_test 1.0 {
+  CREATE TABLE t1(y);
+  PRAGMA journal_mode = wal;
+  INSERT INTO t1 VALUES(1);
+  INSERT INTO t1 VALUES(2);
+  INSERT INTO t1 VALUES(3);
+  INSERT INTO t1 VALUES(4);
+} {wal}
+
+do_test 1.1 {
+  sqlite3 db2 test.db
+  sqlite3 db3 test.db
+
+  execsql {SELECT * FROM sqlite_master} db2
+  execsql {SELECT * FROM sqlite_master} db3
+
+  db2 trans { set snap [sqlite3_snapshot_get_blob db2 main] }
+  db2 eval { SELECT * FROM t1 }
+} {1 2 3 4}
+
+do_test 1.2 {
+  execsql BEGIN db2
+  sqlite3_snapshot_open_blob db2 main $snap
+  db2 eval { SELECT * FROM t1 }
+} {1 2 3 4}
+
+do_test 1.2 {
+  execsql END db2
+  execsql { PRAGMA wal_checkpoint }
+
+  execsql BEGIN db2
+  sqlite3_snapshot_open_blob db2 main $snap
+  db2 eval { SELECT * FROM t1 }
+} {1 2 3 4}
+
+set sz [file size test.db-wal]
+do_test 1.3 {
+  execsql { PRAGMA wal_checkpoint = truncate }
+  file size test.db-wal
+} $sz
+
+do_test 1.4 {
+  execsql BEGIN db3
+  list [catch { sqlite3_snapshot_open_blob db3 main $snap } msg] $msg
+} {0 {}}
+
+do_test 1.5 {
+  db3 eval { SELECT * FROM t1; END }
+} {1 2 3 4}
+
+do_test 1.6 {
+  db2 eval { SELECT * FROM t1; END }
+} {1 2 3 4}
+
+do_test 1.7 {
+  execsql { PRAGMA wal_checkpoint = truncate }
+  file size test.db-wal
+} 0
+
+do_test 1.8 {
+  execsql BEGIN db3
+  list [catch { sqlite3_snapshot_open_blob db3 main $snap } msg] $msg
+} {1 SQLITE_BUSY_SNAPSHOT}
+
+finish_test
+