diff --git a/src/test/modules/Makefile b/src/test/modules/Makefile
index 6167ec1..9b93552 100644
--- a/src/test/modules/Makefile
+++ b/src/test/modules/Makefile
@@ -8,6 +8,7 @@ SUBDIRS = \
 		  brin \
 		  commit_ts \
 		  dummy_seclabel \
+		  snapshot_too_old \
 		  test_ddl_deparse \
 		  test_extensions \
 		  test_parser \
diff --git a/src/test/modules/snapshot_too_old/Makefile b/src/test/modules/snapshot_too_old/Makefile
new file mode 100644
index 0000000..7b9feca
--- /dev/null
+++ b/src/test/modules/snapshot_too_old/Makefile
@@ -0,0 +1,47 @@
+# src/test/modules/snapshot_too_old/Makefile
+
+EXTRA_CLEAN = ./isolation_output
+
+ISOLATIONCHECKS=sto_using_cursor sto_using_select
+
+ifdef USE_PGXS
+PG_CONFIG = pg_config
+PGXS := $(shell $(PG_CONFIG) --pgxs)
+include $(PGXS)
+else
+subdir = src/test/modules/snapshot_too_old
+top_builddir = ../../../..
+include $(top_builddir)/src/Makefile.global
+include $(top_srcdir)/contrib/contrib-global.mk
+endif
+
+# Disabled because these tests require "old_snapshot_threshold" >= 0, which
+# typical installcheck users do not have (e.g. buildfarm clients).
+installcheck:;
+
+# But it can nonetheless be very helpful to run tests on preexisting
+# installation, allow to do so, but only if requested explicitly.
+installcheck-force: isolationcheck-install-force
+
+check: isolationcheck
+
+submake-isolation:
+	$(MAKE) -C $(top_builddir)/src/test/isolation all
+
+submake-test_decoding:
+	$(MAKE) -C $(top_builddir)/src/test/modules/snapshot_too_old
+
+isolationcheck: | submake-isolation temp-install
+	$(MKDIR_P) isolation_output
+	$(pg_isolation_regress_check) \
+	    --temp-config $(top_srcdir)/src/test/modules/snapshot_too_old/sto.conf \
+	    --outputdir=./isolation_output \
+	    $(ISOLATIONCHECKS)
+
+isolationcheck-install-force: all | submake-isolation temp-install
+	$(pg_isolation_regress_installcheck) \
+	    $(ISOLATIONCHECKS)
+
+PHONY: check isolationcheck isolationcheck-install-force
+
+temp-install: EXTRA_INSTALL=src/test/modules/snapshot_too_old
diff --git a/src/test/modules/snapshot_too_old/expected/sto_using_cursor.out b/src/test/modules/snapshot_too_old/expected/sto_using_cursor.out
new file mode 100644
index 0000000..8cc29ec
--- /dev/null
+++ b/src/test/modules/snapshot_too_old/expected/sto_using_cursor.out
@@ -0,0 +1,73 @@
+Parsed test spec with 2 sessions
+
+starting permutation: s1decl s1f1 s1sleep s1f2 s2u
+step s1decl: DECLARE cursor1 CURSOR FOR SELECT c FROM sto1;
+step s1f1: FETCH FIRST FROM cursor1;
+c              
+
+1              
+step s1sleep: SELECT setting, pg_sleep(6) FROM pg_settings WHERE name = 'old_snapshot_threshold';
+setting        pg_sleep       
+
+0                             
+step s1f2: FETCH FIRST FROM cursor1;
+c              
+
+1              
+step s2u: UPDATE sto1 SET c = 1001 WHERE c = 1;
+
+starting permutation: s1decl s1f1 s1sleep s2u s1f2
+step s1decl: DECLARE cursor1 CURSOR FOR SELECT c FROM sto1;
+step s1f1: FETCH FIRST FROM cursor1;
+c              
+
+1              
+step s1sleep: SELECT setting, pg_sleep(6) FROM pg_settings WHERE name = 'old_snapshot_threshold';
+setting        pg_sleep       
+
+0                             
+step s2u: UPDATE sto1 SET c = 1001 WHERE c = 1;
+step s1f2: FETCH FIRST FROM cursor1;
+ERROR:  snapshot too old
+
+starting permutation: s1decl s1f1 s2u s1sleep s1f2
+step s1decl: DECLARE cursor1 CURSOR FOR SELECT c FROM sto1;
+step s1f1: FETCH FIRST FROM cursor1;
+c              
+
+1              
+step s2u: UPDATE sto1 SET c = 1001 WHERE c = 1;
+step s1sleep: SELECT setting, pg_sleep(6) FROM pg_settings WHERE name = 'old_snapshot_threshold';
+setting        pg_sleep       
+
+0                             
+step s1f2: FETCH FIRST FROM cursor1;
+ERROR:  snapshot too old
+
+starting permutation: s1decl s2u s1f1 s1sleep s1f2
+step s1decl: DECLARE cursor1 CURSOR FOR SELECT c FROM sto1;
+step s2u: UPDATE sto1 SET c = 1001 WHERE c = 1;
+step s1f1: FETCH FIRST FROM cursor1;
+c              
+
+1              
+step s1sleep: SELECT setting, pg_sleep(6) FROM pg_settings WHERE name = 'old_snapshot_threshold';
+setting        pg_sleep       
+
+0                             
+step s1f2: FETCH FIRST FROM cursor1;
+ERROR:  snapshot too old
+
+starting permutation: s2u s1decl s1f1 s1sleep s1f2
+step s2u: UPDATE sto1 SET c = 1001 WHERE c = 1;
+step s1decl: DECLARE cursor1 CURSOR FOR SELECT c FROM sto1;
+step s1f1: FETCH FIRST FROM cursor1;
+c              
+
+2              
+step s1sleep: SELECT setting, pg_sleep(6) FROM pg_settings WHERE name = 'old_snapshot_threshold';
+setting        pg_sleep       
+
+0                             
+step s1f2: FETCH FIRST FROM cursor1;
+ERROR:  snapshot too old
diff --git a/src/test/modules/snapshot_too_old/expected/sto_using_select.out b/src/test/modules/snapshot_too_old/expected/sto_using_select.out
new file mode 100644
index 0000000..eb15bc2
--- /dev/null
+++ b/src/test/modules/snapshot_too_old/expected/sto_using_select.out
@@ -0,0 +1,55 @@
+Parsed test spec with 2 sessions
+
+starting permutation: s1f1 s1sleep s1f2 s2u
+step s1f1: SELECT c FROM sto1 ORDER BY c LIMIT 1;
+c              
+
+1              
+step s1sleep: SELECT setting, pg_sleep(6) FROM pg_settings WHERE name = 'old_snapshot_threshold';
+setting        pg_sleep       
+
+0                             
+step s1f2: SELECT c FROM sto1 ORDER BY c LIMIT 1;
+c              
+
+1              
+step s2u: UPDATE sto1 SET c = 1001 WHERE c = 1;
+
+starting permutation: s1f1 s1sleep s2u s1f2
+step s1f1: SELECT c FROM sto1 ORDER BY c LIMIT 1;
+c              
+
+1              
+step s1sleep: SELECT setting, pg_sleep(6) FROM pg_settings WHERE name = 'old_snapshot_threshold';
+setting        pg_sleep       
+
+0                             
+step s2u: UPDATE sto1 SET c = 1001 WHERE c = 1;
+step s1f2: SELECT c FROM sto1 ORDER BY c LIMIT 1;
+ERROR:  snapshot too old
+
+starting permutation: s1f1 s2u s1sleep s1f2
+step s1f1: SELECT c FROM sto1 ORDER BY c LIMIT 1;
+c              
+
+1              
+step s2u: UPDATE sto1 SET c = 1001 WHERE c = 1;
+step s1sleep: SELECT setting, pg_sleep(6) FROM pg_settings WHERE name = 'old_snapshot_threshold';
+setting        pg_sleep       
+
+0                             
+step s1f2: SELECT c FROM sto1 ORDER BY c LIMIT 1;
+ERROR:  snapshot too old
+
+starting permutation: s2u s1f1 s1sleep s1f2
+step s2u: UPDATE sto1 SET c = 1001 WHERE c = 1;
+step s1f1: SELECT c FROM sto1 ORDER BY c LIMIT 1;
+c              
+
+2              
+step s1sleep: SELECT setting, pg_sleep(6) FROM pg_settings WHERE name = 'old_snapshot_threshold';
+setting        pg_sleep       
+
+0                             
+step s1f2: SELECT c FROM sto1 ORDER BY c LIMIT 1;
+ERROR:  snapshot too old
diff --git a/src/test/modules/snapshot_too_old/results/sto_using_cursor.out b/src/test/modules/snapshot_too_old/results/sto_using_cursor.out
new file mode 100644
index 0000000..8cc29ec
--- /dev/null
+++ b/src/test/modules/snapshot_too_old/results/sto_using_cursor.out
@@ -0,0 +1,73 @@
+Parsed test spec with 2 sessions
+
+starting permutation: s1decl s1f1 s1sleep s1f2 s2u
+step s1decl: DECLARE cursor1 CURSOR FOR SELECT c FROM sto1;
+step s1f1: FETCH FIRST FROM cursor1;
+c              
+
+1              
+step s1sleep: SELECT setting, pg_sleep(6) FROM pg_settings WHERE name = 'old_snapshot_threshold';
+setting        pg_sleep       
+
+0                             
+step s1f2: FETCH FIRST FROM cursor1;
+c              
+
+1              
+step s2u: UPDATE sto1 SET c = 1001 WHERE c = 1;
+
+starting permutation: s1decl s1f1 s1sleep s2u s1f2
+step s1decl: DECLARE cursor1 CURSOR FOR SELECT c FROM sto1;
+step s1f1: FETCH FIRST FROM cursor1;
+c              
+
+1              
+step s1sleep: SELECT setting, pg_sleep(6) FROM pg_settings WHERE name = 'old_snapshot_threshold';
+setting        pg_sleep       
+
+0                             
+step s2u: UPDATE sto1 SET c = 1001 WHERE c = 1;
+step s1f2: FETCH FIRST FROM cursor1;
+ERROR:  snapshot too old
+
+starting permutation: s1decl s1f1 s2u s1sleep s1f2
+step s1decl: DECLARE cursor1 CURSOR FOR SELECT c FROM sto1;
+step s1f1: FETCH FIRST FROM cursor1;
+c              
+
+1              
+step s2u: UPDATE sto1 SET c = 1001 WHERE c = 1;
+step s1sleep: SELECT setting, pg_sleep(6) FROM pg_settings WHERE name = 'old_snapshot_threshold';
+setting        pg_sleep       
+
+0                             
+step s1f2: FETCH FIRST FROM cursor1;
+ERROR:  snapshot too old
+
+starting permutation: s1decl s2u s1f1 s1sleep s1f2
+step s1decl: DECLARE cursor1 CURSOR FOR SELECT c FROM sto1;
+step s2u: UPDATE sto1 SET c = 1001 WHERE c = 1;
+step s1f1: FETCH FIRST FROM cursor1;
+c              
+
+1              
+step s1sleep: SELECT setting, pg_sleep(6) FROM pg_settings WHERE name = 'old_snapshot_threshold';
+setting        pg_sleep       
+
+0                             
+step s1f2: FETCH FIRST FROM cursor1;
+ERROR:  snapshot too old
+
+starting permutation: s2u s1decl s1f1 s1sleep s1f2
+step s2u: UPDATE sto1 SET c = 1001 WHERE c = 1;
+step s1decl: DECLARE cursor1 CURSOR FOR SELECT c FROM sto1;
+step s1f1: FETCH FIRST FROM cursor1;
+c              
+
+2              
+step s1sleep: SELECT setting, pg_sleep(6) FROM pg_settings WHERE name = 'old_snapshot_threshold';
+setting        pg_sleep       
+
+0                             
+step s1f2: FETCH FIRST FROM cursor1;
+ERROR:  snapshot too old
diff --git a/src/test/modules/snapshot_too_old/results/sto_using_select.out b/src/test/modules/snapshot_too_old/results/sto_using_select.out
new file mode 100644
index 0000000..eb15bc2
--- /dev/null
+++ b/src/test/modules/snapshot_too_old/results/sto_using_select.out
@@ -0,0 +1,55 @@
+Parsed test spec with 2 sessions
+
+starting permutation: s1f1 s1sleep s1f2 s2u
+step s1f1: SELECT c FROM sto1 ORDER BY c LIMIT 1;
+c              
+
+1              
+step s1sleep: SELECT setting, pg_sleep(6) FROM pg_settings WHERE name = 'old_snapshot_threshold';
+setting        pg_sleep       
+
+0                             
+step s1f2: SELECT c FROM sto1 ORDER BY c LIMIT 1;
+c              
+
+1              
+step s2u: UPDATE sto1 SET c = 1001 WHERE c = 1;
+
+starting permutation: s1f1 s1sleep s2u s1f2
+step s1f1: SELECT c FROM sto1 ORDER BY c LIMIT 1;
+c              
+
+1              
+step s1sleep: SELECT setting, pg_sleep(6) FROM pg_settings WHERE name = 'old_snapshot_threshold';
+setting        pg_sleep       
+
+0                             
+step s2u: UPDATE sto1 SET c = 1001 WHERE c = 1;
+step s1f2: SELECT c FROM sto1 ORDER BY c LIMIT 1;
+ERROR:  snapshot too old
+
+starting permutation: s1f1 s2u s1sleep s1f2
+step s1f1: SELECT c FROM sto1 ORDER BY c LIMIT 1;
+c              
+
+1              
+step s2u: UPDATE sto1 SET c = 1001 WHERE c = 1;
+step s1sleep: SELECT setting, pg_sleep(6) FROM pg_settings WHERE name = 'old_snapshot_threshold';
+setting        pg_sleep       
+
+0                             
+step s1f2: SELECT c FROM sto1 ORDER BY c LIMIT 1;
+ERROR:  snapshot too old
+
+starting permutation: s2u s1f1 s1sleep s1f2
+step s2u: UPDATE sto1 SET c = 1001 WHERE c = 1;
+step s1f1: SELECT c FROM sto1 ORDER BY c LIMIT 1;
+c              
+
+2              
+step s1sleep: SELECT setting, pg_sleep(6) FROM pg_settings WHERE name = 'old_snapshot_threshold';
+setting        pg_sleep       
+
+0                             
+step s1f2: SELECT c FROM sto1 ORDER BY c LIMIT 1;
+ERROR:  snapshot too old
diff --git a/src/test/modules/snapshot_too_old/specs/sto_using_cursor.spec b/src/test/modules/snapshot_too_old/specs/sto_using_cursor.spec
new file mode 100644
index 0000000..eac18ca
--- /dev/null
+++ b/src/test/modules/snapshot_too_old/specs/sto_using_cursor.spec
@@ -0,0 +1,37 @@
+# This test provokes a "snapshot too old" error using a cursor.
+#
+# The sleep is needed because with a threshold of zero a statement could error
+# on changes it made.  With more normal settings no external delay is needed,
+# but we don't want these tests to run long enough to see that, since
+# granularity is in minutes.
+#
+# Since results depend on the value of old_snapshot_threshold, sneak that into
+# the line generated by the sleep, so that a surprising values isn't so hard
+# to identify.
+
+setup
+{
+    CREATE TABLE sto1 (c int NOT NULL);
+    INSERT INTO sto1 SELECT generate_series(1, 1000);
+    CREATE TABLE sto2 (c int NOT NULL);
+}
+setup
+{
+    VACUUM ANALYZE sto1;
+}
+
+teardown
+{
+    DROP TABLE sto1, sto2;
+}
+
+session "s1"
+setup			{ BEGIN ISOLATION LEVEL REPEATABLE READ; }
+step "s1decl"	{ DECLARE cursor1 CURSOR FOR SELECT c FROM sto1; }
+step "s1f1"		{ FETCH FIRST FROM cursor1; }
+step "s1sleep"	{ SELECT setting, pg_sleep(6) FROM pg_settings WHERE name = 'old_snapshot_threshold'; }
+step "s1f2"		{ FETCH FIRST FROM cursor1; }
+teardown		{ COMMIT; }
+
+session "s2"
+step "s2u"		{ UPDATE sto1 SET c = 1001 WHERE c = 1; }
diff --git a/src/test/modules/snapshot_too_old/specs/sto_using_select.spec b/src/test/modules/snapshot_too_old/specs/sto_using_select.spec
new file mode 100644
index 0000000..d7c34f3
--- /dev/null
+++ b/src/test/modules/snapshot_too_old/specs/sto_using_select.spec
@@ -0,0 +1,36 @@
+# This test provokes a "snapshot too old" error using SELECT statements.
+#
+# The sleep is needed because with a threshold of zero a statement could error
+# on changes it made.  With more normal settings no external delay is needed,
+# but we don't want these tests to run long enough to see that, since
+# granularity is in minutes.
+#
+# Since results depend on the value of old_snapshot_threshold, sneak that into
+# the line generated by the sleep, so that a surprising values isn't so hard
+# to identify.
+
+setup
+{
+    CREATE TABLE sto1 (c int NOT NULL);
+    INSERT INTO sto1 SELECT generate_series(1, 1000);
+    CREATE TABLE sto2 (c int NOT NULL);
+}
+setup
+{
+    VACUUM ANALYZE sto1;
+}
+
+teardown
+{
+    DROP TABLE sto1, sto2;
+}
+
+session "s1"
+setup			{ BEGIN ISOLATION LEVEL REPEATABLE READ; }
+step "s1f1"		{ SELECT c FROM sto1 ORDER BY c LIMIT 1; }
+step "s1sleep"	{ SELECT setting, pg_sleep(6) FROM pg_settings WHERE name = 'old_snapshot_threshold'; }
+step "s1f2"		{ SELECT c FROM sto1 ORDER BY c LIMIT 1; }
+teardown		{ COMMIT; }
+
+session "s2"
+step "s2u"		{ UPDATE sto1 SET c = 1001 WHERE c = 1; }
diff --git a/src/test/modules/snapshot_too_old/sto.conf b/src/test/modules/snapshot_too_old/sto.conf
new file mode 100644
index 0000000..ce8048f
--- /dev/null
+++ b/src/test/modules/snapshot_too_old/sto.conf
@@ -0,0 +1,3 @@
+autovacuum = off
+old_snapshot_threshold = 0
+