diff --git a/src/backend/utils/adt/formatting.c b/src/backend/utils/adt/formatting.c
index 2bcc185708..9ec8769eb9 100644
--- a/src/backend/utils/adt/formatting.c
+++ b/src/backend/utils/adt/formatting.c
@@ -622,7 +622,7 @@ typedef enum
 	DCH_Day,
 	DCH_Dy,
 	DCH_D,
-	DCH_FF1,
+	DCH_FF1,					/* FFn codes must be consecutive */
 	DCH_FF2,
 	DCH_FF3,
 	DCH_FF4,
@@ -788,12 +788,12 @@ static const KeyWord DCH_keywords[] = {
 	{"Day", 3, DCH_Day, false, FROM_CHAR_DATE_NONE},
 	{"Dy", 2, DCH_Dy, false, FROM_CHAR_DATE_NONE},
 	{"D", 1, DCH_D, true, FROM_CHAR_DATE_GREGORIAN},
-	{"FF1", 3, DCH_FF1, false, FROM_CHAR_DATE_NONE},	/* F */
-	{"FF2", 3, DCH_FF2, false, FROM_CHAR_DATE_NONE},
-	{"FF3", 3, DCH_FF3, false, FROM_CHAR_DATE_NONE},
-	{"FF4", 3, DCH_FF4, false, FROM_CHAR_DATE_NONE},
-	{"FF5", 3, DCH_FF5, false, FROM_CHAR_DATE_NONE},
-	{"FF6", 3, DCH_FF6, false, FROM_CHAR_DATE_NONE},
+	{"FF1", 3, DCH_FF1, true, FROM_CHAR_DATE_NONE}, /* F */
+	{"FF2", 3, DCH_FF2, true, FROM_CHAR_DATE_NONE},
+	{"FF3", 3, DCH_FF3, true, FROM_CHAR_DATE_NONE},
+	{"FF4", 3, DCH_FF4, true, FROM_CHAR_DATE_NONE},
+	{"FF5", 3, DCH_FF5, true, FROM_CHAR_DATE_NONE},
+	{"FF6", 3, DCH_FF6, true, FROM_CHAR_DATE_NONE},
 	{"FX", 2, DCH_FX, false, FROM_CHAR_DATE_NONE},
 	{"HH24", 4, DCH_HH24, true, FROM_CHAR_DATE_NONE},	/* H */
 	{"HH12", 4, DCH_HH12, true, FROM_CHAR_DATE_NONE},
@@ -844,12 +844,12 @@ static const KeyWord DCH_keywords[] = {
 	{"dd", 2, DCH_DD, true, FROM_CHAR_DATE_GREGORIAN},
 	{"dy", 2, DCH_dy, false, FROM_CHAR_DATE_NONE},
 	{"d", 1, DCH_D, true, FROM_CHAR_DATE_GREGORIAN},
-	{"ff1", 3, DCH_FF1, false, FROM_CHAR_DATE_NONE},	/* f */
-	{"ff2", 3, DCH_FF2, false, FROM_CHAR_DATE_NONE},
-	{"ff3", 3, DCH_FF3, false, FROM_CHAR_DATE_NONE},
-	{"ff4", 3, DCH_FF4, false, FROM_CHAR_DATE_NONE},
-	{"ff5", 3, DCH_FF5, false, FROM_CHAR_DATE_NONE},
-	{"ff6", 3, DCH_FF6, false, FROM_CHAR_DATE_NONE},
+	{"ff1", 3, DCH_FF1, true, FROM_CHAR_DATE_NONE}, /* f */
+	{"ff2", 3, DCH_FF2, true, FROM_CHAR_DATE_NONE},
+	{"ff3", 3, DCH_FF3, true, FROM_CHAR_DATE_NONE},
+	{"ff4", 3, DCH_FF4, true, FROM_CHAR_DATE_NONE},
+	{"ff5", 3, DCH_FF5, true, FROM_CHAR_DATE_NONE},
+	{"ff6", 3, DCH_FF6, true, FROM_CHAR_DATE_NONE},
 	{"fx", 2, DCH_FX, false, FROM_CHAR_DATE_NONE},
 	{"hh24", 4, DCH_HH24, true, FROM_CHAR_DATE_NONE},	/* h */
 	{"hh12", 4, DCH_HH12, true, FROM_CHAR_DATE_NONE},
diff --git a/src/test/regress/expected/horology.out b/src/test/regress/expected/horology.out
index 6d7dd5c988..8a68379578 100644
--- a/src/test/regress/expected/horology.out
+++ b/src/test/regress/expected/horology.out
@@ -3453,6 +3453,17 @@ SELECT i, to_timestamp('2018-11-02 12:34:56.123456', 'YYYY-MM-DD HH24:MI:SS.FF'
 
 SELECT i, to_timestamp('2018-11-02 12:34:56.123456789', 'YYYY-MM-DD HH24:MI:SS.FF' || i) FROM generate_series(1, 6) i;
 ERROR:  date/time field value out of range: "2018-11-02 12:34:56.123456789"
+SELECT i, to_timestamp('20181102123456123456', 'YYYYMMDDHH24MISSFF' || i) FROM generate_series(1, 6) i;
+ i |            to_timestamp             
+---+-------------------------------------
+ 1 | Fri Nov 02 12:34:56.1 2018 PDT
+ 2 | Fri Nov 02 12:34:56.12 2018 PDT
+ 3 | Fri Nov 02 12:34:56.123 2018 PDT
+ 4 | Fri Nov 02 12:34:56.1235 2018 PDT
+ 5 | Fri Nov 02 12:34:56.12346 2018 PDT
+ 6 | Fri Nov 02 12:34:56.123456 2018 PDT
+(6 rows)
+
 SELECT to_date('1 4 1902', 'Q MM YYYY');  -- Q is ignored
   to_date   
 ------------
diff --git a/src/test/regress/sql/horology.sql b/src/test/regress/sql/horology.sql
index 0fe3c783e6..8648163722 100644
--- a/src/test/regress/sql/horology.sql
+++ b/src/test/regress/sql/horology.sql
@@ -558,6 +558,7 @@ SELECT i, to_timestamp('2018-11-02 12:34:56.1234', 'YYYY-MM-DD HH24:MI:SS.FF' ||
 SELECT i, to_timestamp('2018-11-02 12:34:56.12345', 'YYYY-MM-DD HH24:MI:SS.FF' || i) FROM generate_series(1, 6) i;
 SELECT i, to_timestamp('2018-11-02 12:34:56.123456', 'YYYY-MM-DD HH24:MI:SS.FF' || i) FROM generate_series(1, 6) i;
 SELECT i, to_timestamp('2018-11-02 12:34:56.123456789', 'YYYY-MM-DD HH24:MI:SS.FF' || i) FROM generate_series(1, 6) i;
+SELECT i, to_timestamp('20181102123456123456', 'YYYYMMDDHH24MISSFF' || i) FROM generate_series(1, 6) i;
 
 SELECT to_date('1 4 1902', 'Q MM YYYY');  -- Q is ignored
 SELECT to_date('3 4 21 01', 'W MM CC YY');