diff --git a/contrib/btree_gist/btree_gist.sql.in b/contrib/btree_gist/btree_gist.sql.in
index a5f7ae3ffa..c4c260947e 100644
--- a/contrib/btree_gist/btree_gist.sql.in
+++ b/contrib/btree_gist/btree_gist.sql.in
@@ -49,20 +49,20 @@ INPUT  = gbtreekey16_in,
 OUTPUT = gbtreekey16_out
 );
 
-CREATE FUNCTION gbtreekey24_in(cstring)
-RETURNS gbtreekey24
+CREATE FUNCTION gbtreekey32_in(cstring)
+RETURNS gbtreekey32
 AS 'MODULE_PATHNAME', 'gbtreekey_in'
 LANGUAGE 'c' WITH (isstrict);
 
-CREATE FUNCTION gbtreekey24_out(gbtreekey24)
+CREATE FUNCTION gbtreekey32_out(gbtreekey32)
 RETURNS cstring
 AS 'MODULE_PATHNAME', 'gbtreekey_out'
 LANGUAGE 'c' WITH (isstrict);
 
-CREATE TYPE gbtreekey24 (
-INTERNALLENGTH = 24,
-INPUT  = gbtreekey24_in,
-OUTPUT = gbtreekey24_out
+CREATE TYPE gbtreekey32 (
+INTERNALLENGTH = 32,
+INPUT  = gbtreekey32_in,
+OUTPUT = gbtreekey32_out
 );
 
 CREATE FUNCTION gbtreekey_var_in(cstring)
@@ -697,7 +697,7 @@ AS 'MODULE_PATHNAME'
 LANGUAGE 'C';
       
 CREATE FUNCTION gbt_intv_union(bytea, internal)
-RETURNS gbtreekey24
+RETURNS gbtreekey32
 AS 'MODULE_PATHNAME'
 LANGUAGE 'C';
 
@@ -722,7 +722,7 @@ AS
 	FUNCTION	5	gbt_intv_penalty (internal, internal, internal),
 	FUNCTION	6	gbt_intv_picksplit (internal, internal),
 	FUNCTION	7	gbt_intv_same (internal, internal, internal),
-	STORAGE		gbtreekey24;
+	STORAGE		gbtreekey32;
 
 --
 --
diff --git a/contrib/btree_gist/btree_interval.c b/contrib/btree_gist/btree_interval.c
index d3aa4939a3..3c671a3f04 100644
--- a/contrib/btree_gist/btree_interval.c
+++ b/contrib/btree_gist/btree_interval.c
@@ -73,22 +73,14 @@ gbt_intvkey_cmp(const void *a, const void *b)
 static double
 intr2num(const Interval *i)
 {
-	double		ret = 0.0;
-	struct pg_tm tm;
-	fsec_t		fsec;
-
-	interval2tm(*i, &tm, &fsec);
-	ret += (tm.tm_year * 360.0 * 86400.0);
-	ret += (tm.tm_mon * 12.0 * 86400.0);
-	ret += (tm.tm_mday * 86400.0);
-	ret += (tm.tm_hour * 3600.0);
-	ret += (tm.tm_min * 60.0);
-	ret += (tm.tm_sec);
-	ret += (fsec / 1000000.0);
-
-	return (ret);
+	return INTERVAL_TO_SEC(i);
 }
 
+/*
+ * INTERVALSIZE should be the actual size-on-disk of an Interval, as shown
+ * in pg_type.  This might be less than sizeof(Interval) if the compiler
+ * insists on adding alignment padding at the end of the struct.
+ */
 #define INTERVALSIZE 16
 
 static const gbtree_ninfo tinfo =
diff --git a/contrib/btree_gist/btree_time.c b/contrib/btree_gist/btree_time.c
index 9dc3250cf1..02f2664349 100644
--- a/contrib/btree_gist/btree_time.c
+++ b/contrib/btree_gist/btree_time.c
@@ -207,29 +207,24 @@ gbt_time_penalty(PG_FUNCTION_ARGS)
 	timeKEY    *newentry = (timeKEY *) DatumGetPointer(((GISTENTRY *) PG_GETARG_POINTER(1))->key);
 	float	   *result = (float *) PG_GETARG_POINTER(2);
 	Interval   *intr;
-
-#ifdef HAVE_INT64_TIMESTAMP
-	int64		res;
-
-#else
 	double		res;
-#endif
+	double		res2;
 
 	intr = DatumGetIntervalP(DirectFunctionCall2(
 												 time_mi_time,
 										P_TimeADTGetDatum(newentry->upper),
 									 P_TimeADTGetDatum(origentry->upper)));
-
-	/* see interval_larger */
-	res = Max(intr->time + intr->day * 86400 + intr->month * (30 * 86400), 0);
+	res = INTERVAL_TO_SEC(intr);
+	res = Max(res, 0);
 
 	intr = DatumGetIntervalP(DirectFunctionCall2(
 												 time_mi_time,
 									   P_TimeADTGetDatum(origentry->lower),
 									  P_TimeADTGetDatum(newentry->lower)));
+	res2 = INTERVAL_TO_SEC(intr);
+	res2 = Max(res2, 0);
 
-	/* see interval_larger */
-	res += Max(intr->time + intr->day * 86400 + intr->month * (30 * 86400), 0);
+	res += res2;
 
 	*result = 0.0;
 
@@ -240,7 +235,7 @@ gbt_time_penalty(PG_FUNCTION_ARGS)
 									   P_TimeADTGetDatum(origentry->upper),
 									 P_TimeADTGetDatum(origentry->lower)));
 		*result += FLT_MIN;
-		*result += (float) (res / ((double) (res + intr->time + intr->day * 86400 + intr->month * (30 * 86400))));
+		*result += (float) (res / (res + INTERVAL_TO_SEC(intr)));
 		*result *= (FLT_MAX / (((GISTENTRY *) PG_GETARG_POINTER(0))->rel->rd_att->natts + 1));
 	}
 
diff --git a/contrib/btree_gist/btree_utils_num.h b/contrib/btree_gist/btree_utils_num.h
index 8f140953f5..94d4bf7437 100644
--- a/contrib/btree_gist/btree_utils_num.h
+++ b/contrib/btree_gist/btree_utils_num.h
@@ -63,6 +63,24 @@ typedef struct
 } while (0);
 
 
+/*
+ * Convert an Interval to an approximate equivalent number of seconds
+ * (as a double).  Here because we need it for time/timetz as well as
+ * interval.  See interval_cmp_internal for comparison.
+ */
+#ifdef HAVE_INT64_TIMESTAMP
+#define INTERVAL_TO_SEC(ivp) \
+	(((double) (ivp)->time) / ((double) USECS_PER_SEC) + \
+	 (ivp)->day * (24.0 * SECS_PER_HOUR) + \
+	 (ivp)->month * (30.0 * SECS_PER_DAY))
+#else
+#define INTERVAL_TO_SEC(ivp) \
+	((ivp)->time + \
+	 (ivp)->day * (24.0 * SECS_PER_HOUR) + \
+	 (ivp)->month * (30.0 * SECS_PER_DAY))
+#endif
+
+
 extern bool gbt_num_consistent(const GBT_NUMKEY_R * key, const void *query,
 				   const StrategyNumber *strategy, bool is_leaf,
 				   const gbtree_ninfo * tinfo);
diff --git a/contrib/btree_gist/expected/init.out b/contrib/btree_gist/expected/init.out
index 9561fac108..1dbbfd74ec 100644
--- a/contrib/btree_gist/expected/init.out
+++ b/contrib/btree_gist/expected/init.out
@@ -12,9 +12,9 @@ psql:btree_gist.sql:28: NOTICE:  argument type gbtreekey8 is only a shell
 psql:btree_gist.sql:39: NOTICE:  type "gbtreekey16" is not yet defined
 DETAIL:  Creating a shell type definition.
 psql:btree_gist.sql:44: NOTICE:  argument type gbtreekey16 is only a shell
-psql:btree_gist.sql:55: NOTICE:  type "gbtreekey24" is not yet defined
+psql:btree_gist.sql:55: NOTICE:  type "gbtreekey32" is not yet defined
 DETAIL:  Creating a shell type definition.
-psql:btree_gist.sql:60: NOTICE:  argument type gbtreekey24 is only a shell
+psql:btree_gist.sql:60: NOTICE:  argument type gbtreekey32 is only a shell
 psql:btree_gist.sql:71: NOTICE:  type "gbtreekey_var" is not yet defined
 DETAIL:  Creating a shell type definition.
 psql:btree_gist.sql:76: NOTICE:  argument type gbtreekey_var is only a shell