diff --git a/src/backend/utils/adt/numeric.c b/src/backend/utils/adt/numeric.c
index d3d33aae935..14e8895ec70 100644
--- a/src/backend/utils/adt/numeric.c
+++ b/src/backend/utils/adt/numeric.c
@@ -5073,7 +5073,15 @@ numeric_combine(PG_FUNCTION_ARGS)
 	state2 = PG_ARGISNULL(1) ? NULL : (NumericAggState *) PG_GETARG_POINTER(1);
 
 	if (state2 == NULL)
+	{
+		/*
+		 * NULL state2 is easy, just return state1, which we know is already
+		 * in the agg_context
+		 */
+		if (state1 == NULL)
+			PG_RETURN_NULL();
 		PG_RETURN_POINTER(state1);
+	}
 
 	/* manually copy all fields from state2 to state1 */
 	if (state1 == NULL)
@@ -5165,7 +5173,15 @@ numeric_avg_combine(PG_FUNCTION_ARGS)
 	state2 = PG_ARGISNULL(1) ? NULL : (NumericAggState *) PG_GETARG_POINTER(1);
 
 	if (state2 == NULL)
+	{
+		/*
+		 * NULL state2 is easy, just return state1, which we know is already
+		 * in the agg_context
+		 */
+		if (state1 == NULL)
+			PG_RETURN_NULL();
 		PG_RETURN_POINTER(state1);
+	}
 
 	/* manually copy all fields from state2 to state1 */
 	if (state1 == NULL)
@@ -5649,7 +5665,15 @@ numeric_poly_combine(PG_FUNCTION_ARGS)
 	state2 = PG_ARGISNULL(1) ? NULL : (PolyNumAggState *) PG_GETARG_POINTER(1);
 
 	if (state2 == NULL)
+	{
+		/*
+		 * NULL state2 is easy, just return state1, which we know is already
+		 * in the agg_context
+		 */
+		if (state1 == NULL)
+			PG_RETURN_NULL();
 		PG_RETURN_POINTER(state1);
+	}
 
 	/* manually copy all fields from state2 to state1 */
 	if (state1 == NULL)
@@ -5852,7 +5876,15 @@ int8_avg_combine(PG_FUNCTION_ARGS)
 	state2 = PG_ARGISNULL(1) ? NULL : (PolyNumAggState *) PG_GETARG_POINTER(1);
 
 	if (state2 == NULL)
+	{
+		/*
+		 * NULL state2 is easy, just return state1, which we know is already
+		 * in the agg_context
+		 */
+		if (state1 == NULL)
+			PG_RETURN_NULL();
 		PG_RETURN_POINTER(state1);
+	}
 
 	/* manually copy all fields from state2 to state1 */
 	if (state1 == NULL)
diff --git a/src/backend/utils/adt/timestamp.c b/src/backend/utils/adt/timestamp.c
index afd5d7f7502..b57739b7e83 100644
--- a/src/backend/utils/adt/timestamp.c
+++ b/src/backend/utils/adt/timestamp.c
@@ -4035,7 +4035,15 @@ interval_avg_combine(PG_FUNCTION_ARGS)
 	state2 = PG_ARGISNULL(1) ? NULL : (IntervalAggState *) PG_GETARG_POINTER(1);
 
 	if (state2 == NULL)
+	{
+		/*
+		 * NULL state2 is easy, just return state1, which we know is already
+		 * in the agg_context
+		 */
+		if (state1 == NULL)
+			PG_RETURN_NULL();
 		PG_RETURN_POINTER(state1);
+	}
 
 	if (state1 == NULL)
 	{