diff --git a/src/backend/utils/adt/jsonfuncs.c b/src/backend/utils/adt/jsonfuncs.c
index 0273f883d4..c4fd8a9162 100644
--- a/src/backend/utils/adt/jsonfuncs.c
+++ b/src/backend/utils/adt/jsonfuncs.c
@@ -1927,13 +1927,16 @@ each_worker_jsonb(FunctionCallInfo fcinfo, const char *funcname, bool as_text)
 
 	rsi = (ReturnSetInfo *) fcinfo->resultinfo;
 
-	if (!rsi || !IsA(rsi, ReturnSetInfo) ||
-		(rsi->allowedModes & SFRM_Materialize) == 0 ||
+	/* check to see if caller supports us returning a tuplestore */
+	if (rsi == NULL || !IsA(rsi, ReturnSetInfo))
+		ereport(ERROR,
+				(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
+				 errmsg("set-valued function called in context that cannot accept a set")));
+	if (!(rsi->allowedModes & SFRM_Materialize) ||
 		rsi->expectedDesc == NULL)
 		ereport(ERROR,
 				(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
-				 errmsg("set-valued function called in context that "
-						"cannot accept a set")));
+				 errmsg("materialize mode required, but it is not allowed in this context")));
 
 	rsi->returnMode = SFRM_Materialize;
 
@@ -2039,13 +2042,16 @@ each_worker(FunctionCallInfo fcinfo, bool as_text)
 
 	rsi = (ReturnSetInfo *) fcinfo->resultinfo;
 
-	if (!rsi || !IsA(rsi, ReturnSetInfo) ||
-		(rsi->allowedModes & SFRM_Materialize) == 0 ||
+	/* check to see if caller supports us returning a tuplestore */
+	if (rsi == NULL || !IsA(rsi, ReturnSetInfo))
+		ereport(ERROR,
+				(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
+				 errmsg("set-valued function called in context that cannot accept a set")));
+	if (!(rsi->allowedModes & SFRM_Materialize) ||
 		rsi->expectedDesc == NULL)
 		ereport(ERROR,
 				(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
-				 errmsg("set-valued function called in context that "
-						"cannot accept a set")));
+				 errmsg("materialize mode required, but it is not allowed in this context")));
 
 	rsi->returnMode = SFRM_Materialize;
 
@@ -2227,13 +2233,16 @@ elements_worker_jsonb(FunctionCallInfo fcinfo, const char *funcname,
 
 	rsi = (ReturnSetInfo *) fcinfo->resultinfo;
 
-	if (!rsi || !IsA(rsi, ReturnSetInfo) ||
-		(rsi->allowedModes & SFRM_Materialize) == 0 ||
+	/* check to see if caller supports us returning a tuplestore */
+	if (rsi == NULL || !IsA(rsi, ReturnSetInfo))
+		ereport(ERROR,
+				(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
+				 errmsg("set-valued function called in context that cannot accept a set")));
+	if (!(rsi->allowedModes & SFRM_Materialize) ||
 		rsi->expectedDesc == NULL)
 		ereport(ERROR,
 				(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
-				 errmsg("set-valued function called in context that "
-						"cannot accept a set")));
+				 errmsg("materialize mode required, but it is not allowed in this context")));
 
 	rsi->returnMode = SFRM_Materialize;
 
@@ -2336,13 +2345,16 @@ elements_worker(FunctionCallInfo fcinfo, const char *funcname, bool as_text)
 
 	rsi = (ReturnSetInfo *) fcinfo->resultinfo;
 
-	if (!rsi || !IsA(rsi, ReturnSetInfo) ||
-		(rsi->allowedModes & SFRM_Materialize) == 0 ||
+	/* check to see if caller supports us returning a tuplestore */
+	if (rsi == NULL || !IsA(rsi, ReturnSetInfo))
+		ereport(ERROR,
+				(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
+				 errmsg("set-valued function called in context that cannot accept a set")));
+	if (!(rsi->allowedModes & SFRM_Materialize) ||
 		rsi->expectedDesc == NULL)
 		ereport(ERROR,
 				(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
-				 errmsg("set-valued function called in context that "
-						"cannot accept a set")));
+				 errmsg("materialize mode required, but it is not allowed in this context")));
 
 	rsi->returnMode = SFRM_Materialize;
 
diff --git a/src/pl/plperl/plperl.c b/src/pl/plperl/plperl.c
index 3f785b1e8d..0810ec9ccc 100644
--- a/src/pl/plperl/plperl.c
+++ b/src/pl/plperl/plperl.c
@@ -3257,6 +3257,11 @@ plperl_return_next_internal(SV *sv)
 				(errcode(ERRCODE_SYNTAX_ERROR),
 				 errmsg("cannot use return_next in a non-SETOF function")));
 
+	if (rsi == NULL || !IsA(rsi, ReturnSetInfo))
+		ereport(ERROR,
+				(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
+				 errmsg("set-valued function called in context that cannot accept a set")));
+
 	if (!current_call_data->ret_tdesc)
 	{
 		TupleDesc	tupdesc;
@@ -3286,9 +3291,15 @@ plperl_return_next_internal(SV *sv)
 		}
 		else
 		{
+			if (!(rsi->allowedModes & SFRM_Materialize) ||
+				rsi->expectedDesc == NULL)
+				ereport(ERROR,
+					(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
+					errmsg("materialize mode required, but it is not allowed in this context")));
+
 			tupdesc = rsi->expectedDesc;
 			/* Protect assumption below that we return exactly one column */
-			if (tupdesc == NULL || tupdesc->natts != 1)
+			if (tupdesc->natts != 1)
 				elog(ERROR, "expected single-column result descriptor for non-composite SETOF result");
 		}
 
diff --git a/src/pl/plpgsql/src/pl_exec.c b/src/pl/plpgsql/src/pl_exec.c
index 70c4a75295..e346614126 100644
--- a/src/pl/plpgsql/src/pl_exec.c
+++ b/src/pl/plpgsql/src/pl_exec.c
@@ -3645,12 +3645,15 @@ exec_init_tuple_store(PLpgSQL_execstate *estate)
 	/*
 	 * Check caller can handle a set result in the way we want
 	 */
-	if (!rsi || !IsA(rsi, ReturnSetInfo) ||
-		(rsi->allowedModes & SFRM_Materialize) == 0 ||
-		rsi->expectedDesc == NULL)
+	if (rsi == NULL || !IsA(rsi, ReturnSetInfo))
 		ereport(ERROR,
 				(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
 				 errmsg("set-valued function called in context that cannot accept a set")));
+	if (!(rsi->allowedModes & SFRM_Materialize) ||
+		rsi->expectedDesc == NULL)
+		ereport(ERROR,
+				(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
+				 errmsg("materialize mode required, but it is not allowed in this context")));
 
 	/*
 	 * Switch to the right memory context and resource owner for storing the
diff --git a/src/pl/tcl/pltcl.c b/src/pl/tcl/pltcl.c
index 7c045f4560..24c1085de5 100644
--- a/src/pl/tcl/pltcl.c
+++ b/src/pl/tcl/pltcl.c
@@ -3263,7 +3263,16 @@ pltcl_init_tuple_store(pltcl_call_state *call_state)
 	Assert(!call_state->attinmeta);
 
 	/* We expect caller to provide an appropriate result tupdesc */
-	Assert(rsi->expectedDesc);
+	if (rsi == NULL || !IsA(rsi, ReturnSetInfo))
+		ereport(ERROR,
+				(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
+				 errmsg("set-valued function called in context that cannot accept a set")));
+	if (!(rsi->allowedModes & SFRM_Materialize) ||
+		rsi->expectedDesc == NULL)
+		ereport(ERROR,
+				(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
+				 errmsg("materialize mode required, but it is not allowed in this context")));
+
 	call_state->ret_tupdesc = rsi->expectedDesc;
 
 	/*