diff --git a/django/db/backends/postgresql/schema.py b/django/db/backends/postgresql/schema.py
index 75bf331472..c0a785c7e1 100644
--- a/django/db/backends/postgresql/schema.py
+++ b/django/db/backends/postgresql/schema.py
@@ -258,6 +258,25 @@ class DatabaseSchemaEditor(BaseDatabaseSchemaEditor):
                 model, old_field, new_field, new_type, old_collation, new_collation
             )
 
+    def _new_index_should_be_added(self, old_field, new_field):
+        return not (old_field.db_index or old_field.unique) and (
+            new_field.db_index or new_field.unique
+        )
+
+    def _deleted_index_should_be_recreated(
+        self, old_field, new_field, old_type, new_type
+    ):
+        if (
+            not old_field.unique
+            and (
+                not new_field.db_index
+                or (new_field.unique and not new_field.primary_key)
+            )
+        ) or (
+            self._is_changing_type_of_indexed_text_column(old_field, old_type, new_type)
+        ):
+            return True
+
     def _alter_field(
         self,
         model,
@@ -280,14 +299,10 @@ class DatabaseSchemaEditor(BaseDatabaseSchemaEditor):
             strict,
         )
         # Added an index? Create any PostgreSQL-specific indexes.
-        if (
-            (not (old_field.db_index or old_field.unique) and new_field.db_index)
-            or (not old_field.unique and new_field.unique)
-            or (
-                self._is_changing_type_of_indexed_text_column(
-                    old_field, old_type, new_type
-                )
-            )
+        if self._new_index_should_be_added(
+            old_field, new_field
+        ) or self._deleted_index_should_be_recreated(
+            old_field, new_field, old_type, new_type
         ):
             like_index_statement = self._create_like_index_sql(model, new_field)
             if like_index_statement is not None:
diff --git a/tests/migrations/test_operations.py b/tests/migrations/test_operations.py
index 3ac813b899..318cc527c2 100644
--- a/tests/migrations/test_operations.py
+++ b/tests/migrations/test_operations.py
@@ -6213,6 +6213,42 @@ class OperationTests(OperationTestBase):
         self.assertEqual(pony_new.static, 2)
 
 
+class PrimaryKeyOperations(OperationTestBase):
+    def test_slugfields_change_primary_key_operations(self):
+        # Create a model with two fields
+        operation1 = migrations.CreateModel(
+            "SimpleModel",
+            [
+                ("field1", models.SlugField(max_length=20, primary_key=True)),
+                ("field2", models.SlugField(max_length=20)),
+            ],
+        )
+        # Drop field1 primary key constraint - this doesn't fail
+        operation2 = migrations.AlterField(
+            "SimpleModel",
+            "field1",
+            models.SlugField(max_length=20, primary_key=False),
+        )
+        # Add a primary key constraint to field2 - this fails
+        operation3 = migrations.AlterField(
+            "SimpleModel",
+            "field2",
+            models.SlugField(max_length=20, primary_key=True),
+        )
+
+        project_state = ProjectState()
+        with connection.schema_editor() as editor:
+            new_state = project_state.clone()
+            operation1.state_forwards("migrtest", new_state)
+            operation1.database_forwards("migrtest", editor, project_state, new_state)
+            project_state, new_state = new_state, new_state.clone()
+            operation2.state_forwards("migrtest", new_state)
+            operation2.database_forwards("migrtest", editor, project_state, new_state)
+            project_state, new_state = new_state, new_state.clone()
+            operation3.state_forwards("migrtest", new_state)
+            operation3.database_forwards("migrtest", editor, project_state, new_state)
+
+
 class SwappableOperationTests(OperationTestBase):
     """
     Key operations ignore swappable models