diff --git a/src/bin/pg_dump/pg_dump.c b/src/bin/pg_dump/pg_dump.c
index 44d957c038..2d767cb286 100644
--- a/src/bin/pg_dump/pg_dump.c
+++ b/src/bin/pg_dump/pg_dump.c
@@ -16416,7 +16416,7 @@ dumpConstraint(Archive *fout, const ConstraintInfo *coninfo)
 		{
 			appendPQExpBufferStr(q,
 								 coninfo->contype == 'p' ? "PRIMARY KEY" : "UNIQUE");
-			if (indxinfo->indnullsnotdistinct)
+			if (indxinfo->indnullsnotdistinct && coninfo->contype != 'p')
 				appendPQExpBufferStr(q, " NULLS NOT DISTINCT");
 			appendPQExpBufferStr(q, " (");
 			for (k = 0; k < indxinfo->indnkeyattrs; k++)