diff --git a/pyproject.toml b/pyproject.toml
index 18cfea5a..7aef59cc 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -57,6 +57,7 @@ dev = [
     "tomli~=2.0; python_version<'3.11'",
     "types-python-dateutil~=2.8.19",
     "types-requests~=2.29.0",
+    "urllib3<2",  # temporary pin https://github.com/stac-utils/pystac-client/issues/509
 ]
 docs = [
     "Sphinx~=6.2",