diff --git a/src/backend/executor/instrument.c b/src/backend/executor/instrument.c
index edab92a0ebe..4c3930a4f86 100644
--- a/src/backend/executor/instrument.c
+++ b/src/backend/executor/instrument.c
@@ -170,7 +170,7 @@ InstrAggNode(Instrumentation *dst, Instrumentation *add)
 		dst->firsttuple = add->firsttuple;
 	}
 	else if (dst->running && add->running &&
-			 INSTR_TIME_LT(dst->firsttuple, add->firsttuple))
+			 INSTR_TIME_GT(dst->firsttuple, add->firsttuple))
 		dst->firsttuple = add->firsttuple;
 
 	INSTR_TIME_ADD(dst->counter, add->counter);
diff --git a/src/include/portability/instr_time.h b/src/include/portability/instr_time.h
index 490593d1825..87b9ec95531 100644
--- a/src/include/portability/instr_time.h
+++ b/src/include/portability/instr_time.h
@@ -28,6 +28,8 @@
  *
  * INSTR_TIME_ACCUM_DIFF(x, y, z)	x += (y - z)
  *
+ * INSTR_TIME_GT(x, y)				x > y
+ *
  * INSTR_TIME_GET_DOUBLE(t)			convert t to double (in seconds)
  *
  * INSTR_TIME_GET_MILLISEC(t)		convert t to double (in milliseconds)
@@ -184,7 +186,7 @@ GetTimerFrequency(void)
 #define INSTR_TIME_ACCUM_DIFF(x,y,z) \
 	((x).ticks += (y).ticks - (z).ticks)
 
-#define INSTR_TIME_LT(x,y) \
+#define INSTR_TIME_GT(x,y) \
 	((x).ticks > (y).ticks)
 
 #define INSTR_TIME_GET_DOUBLE(t) \