diff --git a/setup.py b/setup.py
index 57a6355..a319787 100644
--- a/setup.py
+++ b/setup.py
@@ -24,7 +24,7 @@
     packages=['spanner_orm', 'spanner_orm.admin'],
     include_package_data=True,
     python_requires='~=3.7',
-    install_requires=['google-cloud-spanner >= 1.6, <2.0.0dev'],
+    install_requires=['google-cloud-spanner >= 1.15.1, <2.0.0dev'],
     tests_require=['absl-py'],
     entry_points={
         'console_scripts': ['spanner-orm = spanner_orm.admin.scripts:main']