diff --git a/changelog.d/16986.misc b/changelog.d/16986.misc
new file mode 100644
index 000000000..0a556ba8b
--- /dev/null
+++ b/changelog.d/16986.misc
@@ -0,0 +1 @@
+Raise poetry-core version cap to 1.9.0.
diff --git a/pyproject.toml b/pyproject.toml
index 2bda9596f..f05546b1c 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -382,7 +382,7 @@ furo = ">=2022.12.7,<2025.0.0"
 # runtime errors caused by build system changes.
 # We are happy to raise these upper bounds upon request,
 # provided we check that it's safe to do so (i.e. that CI passes).
-requires = ["poetry-core>=1.1.0,<=1.8.1", "setuptools_rust>=1.3,<=1.8.1"]
+requires = ["poetry-core>=1.1.0,<=1.9.0", "setuptools_rust>=1.3,<=1.8.1"]
 build-backend = "poetry.core.masonry.api"