diff --git a/backend/db.py b/backend/db.py
index 442798a..a369bfc 100644
--- a/backend/db.py
+++ b/backend/db.py
@@ -307,7 +307,7 @@ def _seed_prompts(conn: Any) -> None:
             SET name = ?, description = ?, category = ?, prompt_type = ?,
                 required_feature = ?, is_system_default = 1, default_template = ?,
                 seed_revision = ?,
-                template = CASE WHEN ? THEN ? ELSE template END,
+                template = CASE WHEN ? = 1 THEN ? ELSE template END,
                 updated = datetime('now')
             WHERE slug = ?
             """,
diff --git a/backend/tests/test_sql_compat.py b/backend/tests/test_sql_compat.py
index bc385a2..037c67f 100644
--- a/backend/tests/test_sql_compat.py
+++ b/backend/tests/test_sql_compat.py
@@ -57,6 +57,9 @@ def main() -> None:
     expect("'?'" in quoted, "question mark inside quotes kept")
     expect(quoted.endswith("%s") or quoted.rstrip().endswith("%s"), "trailing placeholder converted")
 
+    case_sql = adapt_sql("UPDATE t SET x = CASE WHEN ? = 1 THEN ? ELSE x END")
+    expect("CASE WHEN %s = 1 THEN %s ELSE x END" in case_sql, "boolean-safe case placeholder")
+
     parts = split_sql("CREATE TABLE a (id TEXT); CREATE TABLE b (id TEXT);")
     expect(parts == ["CREATE TABLE a (id TEXT)", "CREATE TABLE b (id TEXT)"], "split two statements")
     schema = (ROOT / "schema.sql").read_text(encoding="utf-8")