diff --git a/src/test/modules/test_predtest/test_predtest.c b/src/test/modules/test_predtest/test_predtest.c
index 3b19e0eadc..3e39bc5b89 100644
--- a/src/test/modules/test_predtest/test_predtest.c
+++ b/src/test/modules/test_predtest/test_predtest.c
@@ -74,7 +74,7 @@ test_predtest(PG_FUNCTION_ARGS)
 	if (tupdesc->natts != 2 ||
 		TupleDescAttr(tupdesc, 0)->atttypid != BOOLOID ||
 		TupleDescAttr(tupdesc, 1)->atttypid != BOOLOID)
-		elog(ERROR, "query must yield two boolean columns");
+		elog(ERROR, "test_predtest query must yield two boolean columns");
 
 	s_i_holds = w_i_holds = s_r_holds = w_r_holds = true;
 	for (i = 0; i < SPI_processed; i++)
@@ -124,11 +124,11 @@ test_predtest(PG_FUNCTION_ARGS)
 	 */
 	cplan = SPI_plan_get_cached_plan(spiplan);
 
-	if (list_length(cplan->stmt_list) != 1)
-		elog(ERROR, "failed to decipher query plan");
+	if (cplan == NULL || list_length(cplan->stmt_list) != 1)
+		elog(ERROR, "test_predtest query string must contain exactly one query");
 	stmt = linitial_node(PlannedStmt, cplan->stmt_list);
 	if (stmt->commandType != CMD_SELECT)
-		elog(ERROR, "failed to decipher query plan");
+		elog(ERROR, "test_predtest query must be a SELECT");
 	plan = stmt->planTree;
 	Assert(list_length(plan->targetlist) >= 2);
 	clause1 = linitial_node(TargetEntry, plan->targetlist)->expr;