diff --git a/contrib/pg_trgm/expected/pg_word_trgm.out b/contrib/pg_trgm/expected/pg_word_trgm.out
index bed61c4922..9145e0e3d2 100644
--- a/contrib/pg_trgm/expected/pg_word_trgm.out
+++ b/contrib/pg_trgm/expected/pg_word_trgm.out
@@ -1042,3 +1042,9 @@ select t,word_similarity('Kabankala',t) as sml from test_trgm2 where t %> 'Kaban
  Waikala                          |      0.3
 (89 rows)
 
+-- test unsatisfiable pattern
+select * from test_trgm2 where t ~ '.*$x';
+ t 
+---
+(0 rows)
+
diff --git a/contrib/pg_trgm/sql/pg_word_trgm.sql b/contrib/pg_trgm/sql/pg_word_trgm.sql
index 4b1db9706a..8b91789e65 100644
--- a/contrib/pg_trgm/sql/pg_word_trgm.sql
+++ b/contrib/pg_trgm/sql/pg_word_trgm.sql
@@ -40,3 +40,6 @@ select t,word_similarity('Baykal',t) as sml from test_trgm2 where 'Baykal' <% t
 select t,word_similarity('Kabankala',t) as sml from test_trgm2 where 'Kabankala' <% t order by sml desc, t;
 select t,word_similarity('Baykal',t) as sml from test_trgm2 where t %> 'Baykal' order by sml desc, t;
 select t,word_similarity('Kabankala',t) as sml from test_trgm2 where t %> 'Kabankala' order by sml desc, t;
+
+-- test unsatisfiable pattern
+select * from test_trgm2 where t ~ '.*$x';
diff --git a/contrib/pg_trgm/trgm_regexp.c b/contrib/pg_trgm/trgm_regexp.c
index 547e7c094f..e9da606f16 100644
--- a/contrib/pg_trgm/trgm_regexp.c
+++ b/contrib/pg_trgm/trgm_regexp.c
@@ -1935,9 +1935,7 @@ packGraph(TrgmNFA *trgmNFA, MemoryContext rcontext)
 				arcsCount;
 	HASH_SEQ_STATUS scan_status;
 	TrgmState  *state;
-	TrgmPackArcInfo *arcs,
-			   *p1,
-			   *p2;
+	TrgmPackArcInfo *arcs;
 	TrgmPackedArc *packedArcs;
 	TrgmPackedGraph *result;
 	int			i,
@@ -2009,17 +2007,25 @@ packGraph(TrgmNFA *trgmNFA, MemoryContext rcontext)
 	qsort(arcs, arcIndex, sizeof(TrgmPackArcInfo), packArcInfoCmp);
 
 	/* We could have duplicates because states were merged. Remove them. */
-	/* p1 is probe point, p2 is last known non-duplicate. */
-	p2 = arcs;
-	for (p1 = arcs + 1; p1 < arcs + arcIndex; p1++)
+	if (arcIndex > 1)
 	{
-		if (packArcInfoCmp(p1, p2) > 0)
+		/* p1 is probe point, p2 is last known non-duplicate. */
+		TrgmPackArcInfo *p1,
+				   *p2;
+
+		p2 = arcs;
+		for (p1 = arcs + 1; p1 < arcs + arcIndex; p1++)
 		{
-			p2++;
-			*p2 = *p1;
+			if (packArcInfoCmp(p1, p2) > 0)
+			{
+				p2++;
+				*p2 = *p1;
+			}
 		}
+		arcsCount = (p2 - arcs) + 1;
 	}
-	arcsCount = (p2 - arcs) + 1;
+	else
+		arcsCount = arcIndex;
 
 	/* Create packed representation */
 	result = (TrgmPackedGraph *)