diff --git a/frappe/database/postgres/schema.py b/frappe/database/postgres/schema.py
index fa00c2fe78..946747aa47 100644
--- a/frappe/database/postgres/schema.py
+++ b/frappe/database/postgres/schema.py
@@ -143,12 +143,13 @@ class PostgresTable(DBTable):
 
 		change_nullability = []
 		for col in self.change_nullability:
+			default = col.default or get_not_null_defaults(col.fieldtype)
+			if isinstance(default, str):
+				default = frappe.db.escape(default)
 			change_nullability.append(
 				f"ALTER COLUMN \"{col.fieldname}\" {'SET' if col.not_nullable else 'DROP'} NOT NULL"
 			)
-			change_nullability.append(
-				f'ALTER COLUMN "{col.fieldname}" SET DEFAULT {col.default or frappe.db.escape(col.default)}'
-			)
+			change_nullability.append(f'ALTER COLUMN "{col.fieldname}" SET DEFAULT {default}')
 
 			if col.not_nullable:
 				try:
diff --git a/frappe/database/schema.py b/frappe/database/schema.py
index 621513bf99..497336cd7b 100644
--- a/frappe/database/schema.py
+++ b/frappe/database/schema.py
@@ -209,7 +209,7 @@ class DbColumn:
 			return column_def
 
 		null = True
-		default = ""
+		default = None
 		unique = False
 
 		if self.fieldtype in ("Check", "Int"):
@@ -240,7 +240,7 @@ class DbColumn:
 		if not null:
 			column_def += " NOT NULL"
 
-		if default:
+		if default is not None:
 			column_def += f" DEFAULT {default}"
 
 		if unique: