diff --git a/src/backend/utils/adt/numeric.c b/src/backend/utils/adt/numeric.c
index 553e261ed0..eea4239854 100644
--- a/src/backend/utils/adt/numeric.c
+++ b/src/backend/utils/adt/numeric.c
@@ -5172,11 +5172,21 @@ numeric_stddev_internal(NumericAggState *state,
 				vsumX,
 				vsumX2,
 				vNminus1;
-	const NumericVar *comp;
+	int64		totCount;
 	int			rscale;
 
-	/* Deal with empty input and NaN-input cases */
-	if (state == NULL || (state->N + state->NaNcount) == 0)
+	/*
+	 * Sample stddev and variance are undefined when N <= 1; population stddev
+	 * is undefined when N == 0.  Return NULL in either case (note that NaNs
+	 * count as normal inputs for this purpose).
+	 */
+	if (state == NULL || (totCount = state->N + state->NaNcount) == 0)
+	{
+		*is_null = true;
+		return NULL;
+	}
+
+	if (sample && totCount <= 1)
 	{
 		*is_null = true;
 		return NULL;
@@ -5184,9 +5194,13 @@ numeric_stddev_internal(NumericAggState *state,
 
 	*is_null = false;
 
+	/*
+	 * Deal with NaN inputs.
+	 */
 	if (state->NaNcount > 0)
 		return make_result(&const_nan);
 
+	/* OK, normal calculation applies */
 	init_var(&vN);
 	init_var(&vsumX);
 	init_var(&vsumX2);
@@ -5195,21 +5209,6 @@ numeric_stddev_internal(NumericAggState *state,
 	accum_sum_final(&(state->sumX), &vsumX);
 	accum_sum_final(&(state->sumX2), &vsumX2);
 
-	/*
-	 * Sample stddev and variance are undefined when N <= 1; population stddev
-	 * is undefined when N == 0. Return NULL in either case.
-	 */
-	if (sample)
-		comp = &const_one;
-	else
-		comp = &const_zero;
-
-	if (cmp_var(&vN, comp) <= 0)
-	{
-		*is_null = true;
-		return NULL;
-	}
-
 	init_var(&vNminus1);
 	sub_var(&vN, &const_one, &vNminus1);
 
diff --git a/src/test/regress/expected/aggregates.out b/src/test/regress/expected/aggregates.out
index e4ffa5ee42..3bd184ae29 100644
--- a/src/test/regress/expected/aggregates.out
+++ b/src/test/regress/expected/aggregates.out
@@ -214,13 +214,13 @@ SELECT stddev_pop(3.0::numeric), stddev_samp(4.0::numeric);
 SELECT var_pop('nan'::numeric), var_samp('nan'::numeric);
  var_pop | var_samp 
 ---------+----------
-     NaN |      NaN
+     NaN |         
 (1 row)
 
 SELECT stddev_pop('nan'::numeric), stddev_samp('nan'::numeric);
  stddev_pop | stddev_samp 
 ------------+-------------
-        NaN |         NaN
+        NaN |            
 (1 row)
 
 -- verify correct results for null and NaN inputs