diff --git a/packages/kestrel_analytics_docker/pyproject.toml b/packages/kestrel_analytics_docker/pyproject.toml
index 3b9c9283..7a789dad 100644
--- a/packages/kestrel_analytics_docker/pyproject.toml
+++ b/packages/kestrel_analytics_docker/pyproject.toml
@@ -27,7 +27,7 @@ classifiers = [
 ]
 
 dependencies = [
-    "kestrel_core>=1.8.0",
+    "kestrel_core>=1.8.0, <2",
     "docker>=7.0.0",
 ]
 
diff --git a/packages/kestrel_analytics_python/pyproject.toml b/packages/kestrel_analytics_python/pyproject.toml
index f0ef25ad..88c03f87 100644
--- a/packages/kestrel_analytics_python/pyproject.toml
+++ b/packages/kestrel_analytics_python/pyproject.toml
@@ -27,7 +27,7 @@ classifiers = [
 ]
 
 dependencies = [
-    "kestrel_core>=1.8.0",
+    "kestrel_core>=1.8.0, <2",
 ]
 
 [project.optional-dependencies]
diff --git a/packages/kestrel_datasource_stixbundle/pyproject.toml b/packages/kestrel_datasource_stixbundle/pyproject.toml
index 37a29fa2..18db4d56 100644
--- a/packages/kestrel_datasource_stixbundle/pyproject.toml
+++ b/packages/kestrel_datasource_stixbundle/pyproject.toml
@@ -27,7 +27,7 @@ classifiers = [
 ]
 
 dependencies = [
-    "kestrel_core>=1.8.0",
+    "kestrel_core>=1.8.0, <2",
     "requests>=2.31.0",
     "stix2-matcher>=3.0.0",
 ]
diff --git a/packages/kestrel_datasource_stixshifter/pyproject.toml b/packages/kestrel_datasource_stixshifter/pyproject.toml
index ed767ce0..61a3d441 100644
--- a/packages/kestrel_datasource_stixshifter/pyproject.toml
+++ b/packages/kestrel_datasource_stixshifter/pyproject.toml
@@ -27,7 +27,7 @@ classifiers = [
 ]
 
 dependencies = [
-    "kestrel_core>=1.8.2",
+    "kestrel_core>=1.8.2, <2",
     "lxml==4.9.4", # Python 3.8 on mac error >5.0.0; stackoverflow #75442675
     "requests>=2.31.0",
     "nest-asyncio>=1.6.0",