diff --git a/src/backend/catalog/pg_operator.c b/src/backend/catalog/pg_operator.c
index 95918a77a1..b0570c33b6 100644
--- a/src/backend/catalog/pg_operator.c
+++ b/src/backend/catalog/pg_operator.c
@@ -57,8 +57,7 @@ static Oid	OperatorShellMake(const char *operatorName,
 static Oid	get_other_operator(List *otherOp,
 							   Oid otherLeftTypeId, Oid otherRightTypeId,
 							   const char *operatorName, Oid operatorNamespace,
-							   Oid leftTypeId, Oid rightTypeId,
-							   bool isCommutator);
+							   Oid leftTypeId, Oid rightTypeId);
 
 
 /*
@@ -442,8 +441,7 @@ OperatorCreate(const char *operatorName,
 		commutatorId = get_other_operator(commutatorName,
 										  rightTypeId, leftTypeId,
 										  operatorName, operatorNamespace,
-										  leftTypeId, rightTypeId,
-										  true);
+										  leftTypeId, rightTypeId);
 
 		/* Permission check: must own other operator */
 		if (OidIsValid(commutatorId) &&
@@ -467,8 +465,19 @@ OperatorCreate(const char *operatorName,
 		negatorId = get_other_operator(negatorName,
 									   leftTypeId, rightTypeId,
 									   operatorName, operatorNamespace,
-									   leftTypeId, rightTypeId,
-									   false);
+									   leftTypeId, rightTypeId);
+
+		/*
+		 * Prevent self negation as it doesn't make sense. When self negating,
+		 * get_other_operator returns InvalidOid when creating a new operator
+		 * and the OID of the operator we are 'creating' when upgrading a
+		 * shell operator.
+		 */
+
+		if (!OidIsValid(negatorId) || operatorObjectId == negatorId)
+			ereport(ERROR,
+					(errcode(ERRCODE_INVALID_FUNCTION_DEFINITION),
+					 errmsg("operator cannot be its own negator")));
 
 		/* Permission check: must own other operator */
 		if (OidIsValid(negatorId) &&
@@ -584,7 +593,7 @@ OperatorCreate(const char *operatorName,
 static Oid
 get_other_operator(List *otherOp, Oid otherLeftTypeId, Oid otherRightTypeId,
 				   const char *operatorName, Oid operatorNamespace,
-				   Oid leftTypeId, Oid rightTypeId, bool isCommutator)
+				   Oid leftTypeId, Oid rightTypeId)
 {
 	Oid			other_oid;
 	bool		otherDefined;
@@ -611,14 +620,7 @@ get_other_operator(List *otherOp, Oid otherLeftTypeId, Oid otherRightTypeId,
 		otherLeftTypeId == leftTypeId &&
 		otherRightTypeId == rightTypeId)
 	{
-		/*
-		 * self-linkage to this operator; caller will fix later. Note that
-		 * only self-linkage for commutation makes sense.
-		 */
-		if (!isCommutator)
-			ereport(ERROR,
-					(errcode(ERRCODE_INVALID_FUNCTION_DEFINITION),
-					 errmsg("operator cannot be its own negator or sort operator")));
+		/* self-linkage to this operator; caller will fix later. */
 		return InvalidOid;
 	}
 
diff --git a/src/test/regress/expected/create_operator.out b/src/test/regress/expected/create_operator.out
index f71b601f2d..49070ce90f 100644
--- a/src/test/regress/expected/create_operator.out
+++ b/src/test/regress/expected/create_operator.out
@@ -260,6 +260,42 @@ CREATE OPERATOR #*# (
 );
 ERROR:  permission denied for type type_op6
 ROLLBACK;
+-- Should fail. An operator cannot have a self negator.
+BEGIN TRANSACTION;
+CREATE FUNCTION create_op_test_fn(boolean, boolean)
+RETURNS boolean AS $$
+    SELECT NULL::BOOLEAN;
+$$ LANGUAGE sql IMMUTABLE;
+CREATE OPERATOR === (
+    leftarg = boolean,
+    rightarg = boolean,
+    procedure = create_op_test_fn,
+    negator = ===
+);
+ERROR:  operator cannot be its own negator
+ROLLBACK;
+-- Should fail. An operator cannot have a self negator. Here we test that when
+-- 'creating' an existing shell operator, it checks the negator is not self.
+BEGIN TRANSACTION;
+CREATE FUNCTION create_op_test_fn(boolean, boolean)
+RETURNS boolean AS $$
+    SELECT NULL::BOOLEAN;
+$$ LANGUAGE sql IMMUTABLE;
+-- create a shell operator for ===!!! by referencing it as a commutator
+CREATE OPERATOR === (
+    leftarg = boolean,
+    rightarg = boolean,
+    procedure = create_op_test_fn,
+    commutator = ===!!!
+);
+CREATE OPERATOR ===!!! (
+    leftarg = boolean,
+    rightarg = boolean,
+    procedure = create_op_test_fn,
+    negator = ===!!!
+);
+ERROR:  operator cannot be its own negator
+ROLLBACK;
 -- invalid: non-lowercase quoted identifiers
 CREATE OPERATOR ===
 (
diff --git a/src/test/regress/sql/create_operator.sql b/src/test/regress/sql/create_operator.sql
index f53e24db3c..168cad3814 100644
--- a/src/test/regress/sql/create_operator.sql
+++ b/src/test/regress/sql/create_operator.sql
@@ -210,6 +210,42 @@ CREATE OPERATOR #*# (
 );
 ROLLBACK;
 
+-- Should fail. An operator cannot have a self negator.
+BEGIN TRANSACTION;
+CREATE FUNCTION create_op_test_fn(boolean, boolean)
+RETURNS boolean AS $$
+    SELECT NULL::BOOLEAN;
+$$ LANGUAGE sql IMMUTABLE;
+CREATE OPERATOR === (
+    leftarg = boolean,
+    rightarg = boolean,
+    procedure = create_op_test_fn,
+    negator = ===
+);
+ROLLBACK;
+
+-- Should fail. An operator cannot have a self negator. Here we test that when
+-- 'creating' an existing shell operator, it checks the negator is not self.
+BEGIN TRANSACTION;
+CREATE FUNCTION create_op_test_fn(boolean, boolean)
+RETURNS boolean AS $$
+    SELECT NULL::BOOLEAN;
+$$ LANGUAGE sql IMMUTABLE;
+-- create a shell operator for ===!!! by referencing it as a commutator
+CREATE OPERATOR === (
+    leftarg = boolean,
+    rightarg = boolean,
+    procedure = create_op_test_fn,
+    commutator = ===!!!
+);
+CREATE OPERATOR ===!!! (
+    leftarg = boolean,
+    rightarg = boolean,
+    procedure = create_op_test_fn,
+    negator = ===!!!
+);
+ROLLBACK;
+
 -- invalid: non-lowercase quoted identifiers
 CREATE OPERATOR ===
 (