diff --git a/internal/plan/rewrite.go b/internal/plan/rewrite.go
index 6549b053..a32185ae 100644
--- a/internal/plan/rewrite.go
+++ b/internal/plan/rewrite.go
@@ -293,6 +293,10 @@ func generateColumnNotNullRewrite(_ *diff.ColumnDiff, path string) []RewriteStep
 	setNotNullSQL := fmt.Sprintf("ALTER TABLE %s ALTER COLUMN %s SET NOT NULL;",
 		tableName, column)
 
+	// Step 4: Drop CHECK constraint
+	dropConstraintSQL := fmt.Sprintf("ALTER TABLE %s DROP CONSTRAINT %s;",
+		tableName, ir.QuoteIdentifier(constraintName))
+
 	return []RewriteStep{
 		{
 			SQL:                 addConstraintSQL,
@@ -306,6 +310,10 @@ func generateColumnNotNullRewrite(_ *diff.ColumnDiff, path string) []RewriteStep
 			SQL:                 setNotNullSQL,
 			CanRunInTransaction: true,
 		},
+		{
+			SQL:                 dropConstraintSQL,
+			CanRunInTransaction: true,
+		},
 	}
 }
 
diff --git a/testdata/diff/online/add_not_null/plan.json b/testdata/diff/online/add_not_null/plan.json
index 4d06b467..ad75e5d2 100644
--- a/testdata/diff/online/add_not_null/plan.json
+++ b/testdata/diff/online/add_not_null/plan.json
@@ -25,6 +25,12 @@
           "type": "table.column",
           "operation": "alter",
           "path": "public.users.email"
+        },
+        {
+          "sql": "ALTER TABLE users DROP CONSTRAINT email_not_null;",
+          "type": "table.column",
+          "operation": "alter",
+          "path": "public.users.email"
         }
       ]
     }
diff --git a/testdata/diff/online/add_not_null/plan.sql b/testdata/diff/online/add_not_null/plan.sql
index 582bb35c..5429fe86 100644
--- a/testdata/diff/online/add_not_null/plan.sql
+++ b/testdata/diff/online/add_not_null/plan.sql
@@ -3,3 +3,5 @@ ALTER TABLE users ADD CONSTRAINT email_not_null CHECK (email IS NOT NULL) NOT VA
 ALTER TABLE users VALIDATE CONSTRAINT email_not_null;
 
 ALTER TABLE users ALTER COLUMN email SET NOT NULL;
+
+ALTER TABLE users DROP CONSTRAINT email_not_null;
diff --git a/testdata/diff/online/add_not_null/plan.txt b/testdata/diff/online/add_not_null/plan.txt
index 828240a3..7e8e867b 100644
--- a/testdata/diff/online/add_not_null/plan.txt
+++ b/testdata/diff/online/add_not_null/plan.txt
@@ -15,3 +15,5 @@ ALTER TABLE users ADD CONSTRAINT email_not_null CHECK (email IS NOT NULL) NOT VA
 ALTER TABLE users VALIDATE CONSTRAINT email_not_null;
 
 ALTER TABLE users ALTER COLUMN email SET NOT NULL;
+
+ALTER TABLE users DROP CONSTRAINT email_not_null;