diff --git a/contrib/test_shm_mq/expected/test_shm_mq.out b/contrib/test_shm_mq/expected/test_shm_mq.out
index dd9891c7c7..c4858b0c20 100644
--- a/contrib/test_shm_mq/expected/test_shm_mq.out
+++ b/contrib/test_shm_mq/expected/test_shm_mq.out
@@ -4,13 +4,31 @@ CREATE EXTENSION test_shm_mq;
 -- the operations complete without crashing or hanging and that none of their
 -- internal sanity tests fail.
 --
-SELECT test_shm_mq(32768, (select string_agg(chr(32+(random()*96)::int), '') from generate_series(1,400)), 10000, 1);
+SELECT test_shm_mq(1024, '', 2000, 1);
  test_shm_mq 
 -------------
  
 (1 row)
 
-SELECT test_shm_mq_pipelined(16384, (select string_agg(chr(32+(random()*96)::int), '') from generate_series(1,270000)), 200, 3);
+SELECT test_shm_mq(1024, 'a', 2001, 1);
+ test_shm_mq 
+-------------
+ 
+(1 row)
+
+SELECT test_shm_mq(32768, (select string_agg(chr(32+(random()*95)::int), '') from generate_series(1,(100+900*random())::int)), 10000, 1);
+ test_shm_mq 
+-------------
+ 
+(1 row)
+
+SELECT test_shm_mq(100, (select string_agg(chr(32+(random()*95)::int), '') from generate_series(1,(100+200*random())::int)), 10000, 1);
+ test_shm_mq 
+-------------
+ 
+(1 row)
+
+SELECT test_shm_mq_pipelined(16384, (select string_agg(chr(32+(random()*95)::int), '') from generate_series(1,270000)), 200, 3);
  test_shm_mq_pipelined 
 -----------------------
  
diff --git a/contrib/test_shm_mq/sql/test_shm_mq.sql b/contrib/test_shm_mq/sql/test_shm_mq.sql
index 1366df17ea..9de19d304a 100644
--- a/contrib/test_shm_mq/sql/test_shm_mq.sql
+++ b/contrib/test_shm_mq/sql/test_shm_mq.sql
@@ -5,5 +5,8 @@ CREATE EXTENSION test_shm_mq;
 -- the operations complete without crashing or hanging and that none of their
 -- internal sanity tests fail.
 --
-SELECT test_shm_mq(32768, (select string_agg(chr(32+(random()*96)::int), '') from generate_series(1,400)), 10000, 1);
-SELECT test_shm_mq_pipelined(16384, (select string_agg(chr(32+(random()*96)::int), '') from generate_series(1,270000)), 200, 3);
+SELECT test_shm_mq(1024, '', 2000, 1);
+SELECT test_shm_mq(1024, 'a', 2001, 1);
+SELECT test_shm_mq(32768, (select string_agg(chr(32+(random()*95)::int), '') from generate_series(1,(100+900*random())::int)), 10000, 1);
+SELECT test_shm_mq(100, (select string_agg(chr(32+(random()*95)::int), '') from generate_series(1,(100+200*random())::int)), 10000, 1);
+SELECT test_shm_mq_pipelined(16384, (select string_agg(chr(32+(random()*95)::int), '') from generate_series(1,270000)), 200, 3);