diff --git a/requirements.txt b/requirements.txt
index 99e3306e..a865b3f4 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -1,4 +1,4 @@
-apscheduler>=3.3.0
+apscheduler>=3.3.0,<4.0
 aws-requests-auth>=0.3.0
 sortedcontainers>=2.2.2
 boto3>=1.4.4
diff --git a/setup.py b/setup.py
index e0e320ee..85a102c6 100644
--- a/setup.py
+++ b/setup.py
@@ -27,7 +27,7 @@
     packages=find_packages(),
     package_data={'elastalert': ['schema.yaml', 'es_mappings/**/*.json']},
     install_requires=[
-        'apscheduler>=3.3.0',
+        'apscheduler>=3.3.0,<4.0',
         'aws-requests-auth>=0.3.0',
         'sortedcontainers>=2.2.2',
         'boto3>=1.4.4',