diff --git a/src/backend/executor/nodeModifyTable.c b/src/backend/executor/nodeModifyTable.c
index 214482d193d..3a4ce5c32f8 100644
--- a/src/backend/executor/nodeModifyTable.c
+++ b/src/backend/executor/nodeModifyTable.c
@@ -129,19 +129,10 @@ ExecCheckPlanOutput(Relation resultRel, List *targetList)
 		attr = TupleDescAttr(resultDesc, attno);
 		attno++;
 
-		if (!attr->attisdropped)
-		{
-			/* Normal case: demand type match */
-			if (exprType((Node *) tle->expr) != attr->atttypid)
-				ereport(ERROR,
-						(errcode(ERRCODE_DATATYPE_MISMATCH),
-						 errmsg("table row type and query-specified row type do not match"),
-						 errdetail("Table has type %s at ordinal position %d, but query expects %s.",
-								   format_type_be(attr->atttypid),
-								   attno,
-								   format_type_be(exprType((Node *) tle->expr)))));
-		}
-		else
+		/*
+		 * Special cases here should match planner's expand_insert_targetlist.
+		 */
+		if (attr->attisdropped)
 		{
 			/*
 			 * For a dropped column, we can't check atttypid (it's likely 0).
@@ -156,6 +147,35 @@ ExecCheckPlanOutput(Relation resultRel, List *targetList)
 						 errdetail("Query provides a value for a dropped column at ordinal position %d.",
 								   attno)));
 		}
+		else if (attr->attgenerated)
+		{
+			/*
+			 * For a generated column, the planner will have inserted a null
+			 * of the column's base type (to avoid possibly failing on domain
+			 * not-null constraints).  It doesn't seem worth insisting on that
+			 * exact type though, since a null value is type-independent.  As
+			 * above, just insist on *some* NULL constant.
+			 */
+			if (!IsA(tle->expr, Const) ||
+				!((Const *) tle->expr)->constisnull)
+				ereport(ERROR,
+						(errcode(ERRCODE_DATATYPE_MISMATCH),
+						 errmsg("table row type and query-specified row type do not match"),
+						 errdetail("Query provides a value for a generated column at ordinal position %d.",
+								   attno)));
+		}
+		else
+		{
+			/* Normal case: demand type match */
+			if (exprType((Node *) tle->expr) != attr->atttypid)
+				ereport(ERROR,
+						(errcode(ERRCODE_DATATYPE_MISMATCH),
+						 errmsg("table row type and query-specified row type do not match"),
+						 errdetail("Table has type %s at ordinal position %d, but query expects %s.",
+								   format_type_be(attr->atttypid),
+								   attno,
+								   format_type_be(exprType((Node *) tle->expr)))));
+		}
 	}
 	if (attno != resultDesc->natts)
 		ereport(ERROR,
diff --git a/src/backend/optimizer/prep/preptlist.c b/src/backend/optimizer/prep/preptlist.c
index e9151c9589a..125fcf01390 100644
--- a/src/backend/optimizer/prep/preptlist.c
+++ b/src/backend/optimizer/prep/preptlist.c
@@ -44,6 +44,7 @@
 #include "optimizer/tlist.h"
 #include "parser/parse_coerce.h"
 #include "parser/parsetree.h"
+#include "utils/lsyscache.h"
 #include "utils/rel.h"
 
 static List *expand_insert_targetlist(PlannerInfo *root, List *tlist,
@@ -334,9 +335,8 @@ expand_insert_targetlist(PlannerInfo *root, List *tlist, Relation rel)
 			 *
 			 * INSERTs should insert NULL in this case.  (We assume the
 			 * rewriter would have inserted any available non-NULL default
-			 * value.)  Also, if the column isn't dropped, apply any domain
-			 * constraints that might exist --- this is to catch domain NOT
-			 * NULL.
+			 * value.)  Also, normally we must apply any domain constraints
+			 * that might exist --- this is to catch domain NOT NULL.
 			 *
 			 * When generating a NULL constant for a dropped column, we label
 			 * it INT4 (any other guaranteed-to-exist datatype would do as
@@ -346,21 +346,17 @@ expand_insert_targetlist(PlannerInfo *root, List *tlist, Relation rel)
 			 * representation is datatype-independent.  This could perhaps
 			 * confuse code comparing the finished plan to the target
 			 * relation, however.
+			 *
+			 * Another exception is that if the column is generated, the value
+			 * we produce here will be ignored, and we don't want to risk
+			 * throwing an error.  So in that case we *don't* want to apply
+			 * domain constraints, so we must produce a NULL of the base type.
+			 * Again, code comparing the finished plan to the target relation
+			 * must account for this.
 			 */
 			Node	   *new_expr;
 
-			if (!att_tup->attisdropped)
-			{
-				new_expr = coerce_null_to_domain(att_tup->atttypid,
-												 att_tup->atttypmod,
-												 att_tup->attcollation,
-												 att_tup->attlen,
-												 att_tup->attbyval);
-				/* Must run expression preprocessing on any non-const nodes */
-				if (!IsA(new_expr, Const))
-					new_expr = eval_const_expressions(root, new_expr);
-			}
-			else
+			if (att_tup->attisdropped)
 			{
 				/* Insert NULL for dropped column */
 				new_expr = (Node *) makeConst(INT4OID,
@@ -371,6 +367,33 @@ expand_insert_targetlist(PlannerInfo *root, List *tlist, Relation rel)
 											  true, /* isnull */
 											  true /* byval */ );
 			}
+			else if (att_tup->attgenerated)
+			{
+				/* Generated column, insert a NULL of the base type */
+				Oid			baseTypeId = att_tup->atttypid;
+				int32		baseTypeMod = att_tup->atttypmod;
+
+				baseTypeId = getBaseTypeAndTypmod(baseTypeId, &baseTypeMod);
+				new_expr = (Node *) makeConst(baseTypeId,
+											  baseTypeMod,
+											  att_tup->attcollation,
+											  att_tup->attlen,
+											  (Datum) 0,
+											  true, /* isnull */
+											  att_tup->attbyval);
+			}
+			else
+			{
+				/* Normal column, insert a NULL of the column datatype */
+				new_expr = coerce_null_to_domain(att_tup->atttypid,
+												 att_tup->atttypmod,
+												 att_tup->attcollation,
+												 att_tup->attlen,
+												 att_tup->attbyval);
+				/* Must run expression preprocessing on any non-const nodes */
+				if (!IsA(new_expr, Const))
+					new_expr = eval_const_expressions(root, new_expr);
+			}
 
 			new_tle = makeTargetEntry((Expr *) new_expr,
 									  attrno,
diff --git a/src/test/regress/expected/generated.out b/src/test/regress/expected/generated.out
index dccf0ddc522..74680d385be 100644
--- a/src/test/regress/expected/generated.out
+++ b/src/test/regress/expected/generated.out
@@ -685,6 +685,11 @@ CREATE TABLE gtest24 (a int PRIMARY KEY, b gtestdomain1 GENERATED ALWAYS AS (a *
 INSERT INTO gtest24 (a) VALUES (4);  -- ok
 INSERT INTO gtest24 (a) VALUES (6);  -- error
 ERROR:  value for domain gtestdomain1 violates check constraint "gtestdomain1_check"
+CREATE DOMAIN gtestdomainnn AS int CHECK (VALUE IS NOT NULL);
+CREATE TABLE gtest24nn (a int, b gtestdomainnn GENERATED ALWAYS AS (a * 2) STORED);
+INSERT INTO gtest24nn (a) VALUES (4);  -- ok
+INSERT INTO gtest24nn (a) VALUES (NULL);  -- error
+ERROR:  value for domain gtestdomainnn violates check constraint "gtestdomainnn_check"
 -- typed tables (currently not supported)
 CREATE TYPE gtest_type AS (f1 integer, f2 text, f3 bigint);
 CREATE TABLE gtest28 OF gtest_type (f1 WITH OPTIONS GENERATED ALWAYS AS (f2 *2) STORED);
diff --git a/src/test/regress/sql/generated.sql b/src/test/regress/sql/generated.sql
index 4d2fc9c5ae8..06faa1d72a6 100644
--- a/src/test/regress/sql/generated.sql
+++ b/src/test/regress/sql/generated.sql
@@ -361,6 +361,11 @@ CREATE TABLE gtest24 (a int PRIMARY KEY, b gtestdomain1 GENERATED ALWAYS AS (a *
 INSERT INTO gtest24 (a) VALUES (4);  -- ok
 INSERT INTO gtest24 (a) VALUES (6);  -- error
 
+CREATE DOMAIN gtestdomainnn AS int CHECK (VALUE IS NOT NULL);
+CREATE TABLE gtest24nn (a int, b gtestdomainnn GENERATED ALWAYS AS (a * 2) STORED);
+INSERT INTO gtest24nn (a) VALUES (4);  -- ok
+INSERT INTO gtest24nn (a) VALUES (NULL);  -- error
+
 -- typed tables (currently not supported)
 CREATE TYPE gtest_type AS (f1 integer, f2 text, f3 bigint);
 CREATE TABLE gtest28 OF gtest_type (f1 WITH OPTIONS GENERATED ALWAYS AS (f2 *2) STORED);