diff --git a/pyproject.toml b/pyproject.toml
index 9f2294d4bf..ca7527868d 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -65,6 +65,10 @@ dev = [
     # it depends on the 'InvalidCatalogIntegrationConfigError' class that only exists as of dbt-adapters==1.16.6
     # so we exclude it to prevent failures and hope that upstream releases a new version with the correct constraint
     "dbt-snowflake!=1.10.1",
+    # fastjsonschema 2.22+ uses PEP 604 type hints and now requires Python >=3.10
+    # (upstream #211 / #213). Keep 3.9 on the 2.21 line; pulled in via
+    # dbt-bigquery → nbformat.
+    "fastjsonschema<2.22; python_version<'3.10'",
     "dbt-athena-community",
     "dbt-clickhouse",
     "dbt-databricks",