diff --git a/doc/src/sgml/ref/explain.sgml b/doc/src/sgml/ref/explain.sgml
index 49c61cce69..26809d68d5 100644
--- a/doc/src/sgml/ref/explain.sgml
+++ b/doc/src/sgml/ref/explain.sgml
@@ -256,8 +256,9 @@ ROLLBACK;
     <listitem>
      <para>
       Include information on memory consumption by the query planning phase.
-      Report the precise amount of storage used by planner in-memory
-      structures, and total memory considering allocation overhead.
+      Specifically, include the precise amount of storage used by planner
+      in-memory structures, as well as total memory considering allocation
+      overhead.
       The parameter defaults to <literal>FALSE</literal>.
      </para>
     </listitem>
diff --git a/src/backend/commands/explain.c b/src/backend/commands/explain.c
index 0a18a7abd8..2fa93998a3 100644
--- a/src/backend/commands/explain.c
+++ b/src/backend/commands/explain.c
@@ -660,7 +660,7 @@ ExplainOnePlan(PlannedStmt *plannedstmt, IntoClause *into, ExplainState *es,
 		ExplainPropertyFloat("Planning Time", "ms", 1000.0 * plantime, 3, es);
 	}
 
-	if (mem_counts)
+	if (es->memory && mem_counts != NULL)
 	{
 		ExplainOpenGroup("Planner Memory", "Planner Memory", true, es);
 		show_planner_memory(es, mem_counts);
@@ -3813,9 +3813,9 @@ show_planner_memory(ExplainState *es,
 	if (es->format == EXPLAIN_FORMAT_TEXT)
 	{
 		appendStringInfo(es->str,
-						 "Planner Memory: used=%zu bytes allocated=%zu bytes",
-						 mem_counts->totalspace - mem_counts->freespace,
-						 mem_counts->totalspace);
+						 "Planner Memory: used=%lld bytes allocated=%lld bytes",
+						 (long long) (mem_counts->totalspace - mem_counts->freespace),
+						 (long long) mem_counts->totalspace);
 		appendStringInfoChar(es->str, '\n');
 	}
 	else
diff --git a/src/backend/commands/prepare.c b/src/backend/commands/prepare.c
index 7e947e023b..e1577c791a 100644
--- a/src/backend/commands/prepare.c
+++ b/src/backend/commands/prepare.c
@@ -590,9 +590,12 @@ ExplainExecuteQuery(ExecuteStmt *execstmt, IntoClause *into, ExplainState *es,
 	if (es->memory)
 	{
 		/*
-		 * Create a new memory context to measure planner's memory consumption
-		 * accurately. We should use the same type of memory context as the
-		 * planner would use. That's usually AllocSet but ensure that.
+		 * In order to measure planner's memory consumption accurately, create
+		 * a separate AllocSet memory context.
+		 *
+		 * XXX if planner is called under some other memory context type, this
+		 * code overrides that.  Do we need support to create context of
+		 * programmatically determined type?
 		 */
 		Assert(IsA(CurrentMemoryContext, AllocSetContext));
 		planner_ctx = AllocSetContextCreate(CurrentMemoryContext,