diff --git a/.changeset/local-properties-align.md b/.changeset/local-properties-align.md
new file mode 100644
index 0000000..0876bba
--- /dev/null
+++ b/.changeset/local-properties-align.md
@@ -0,0 +1,6 @@
+---
+"posthog-ruby": patch
+"posthog-rails": patch
+---
+
+Align local `is_set` and `is_not_set` evaluation with partial property context.
diff --git a/lib/posthog/feature_flags.rb b/lib/posthog/feature_flags.rb
index ef2a65e..7c6f12e 100644
--- a/lib/posthog/feature_flags.rb
+++ b/lib/posthog/feature_flags.rb
@@ -614,7 +614,6 @@ def self.semver_wildcard_bounds(value)
 
     def self.match_property(property, property_values, cohort_properties = {})
       # only looks for matches where key exists in property_values
-      # doesn't support operator is_not_set
 
       PostHog::Utils.symbolize_keys! property
       PostHog::Utils.symbolize_keys! property_values
@@ -629,7 +628,7 @@ def self.match_property(property, property_values, cohort_properties = {})
       if !property_values.key?(key)
         raise InconclusiveMatchError, "Property #{key} not found in property_values"
       elsif operator == 'is_not_set'
-        raise InconclusiveMatchError, 'Operator is_not_set not supported'
+        return false
       end
 
       override_value = property_values[key]
diff --git a/spec/posthog/feature_flag_spec.rb b/spec/posthog/feature_flag_spec.rb
index ab7f9ec..5d965c9 100644
--- a/spec/posthog/feature_flag_spec.rb
+++ b/spec/posthog/feature_flag_spec.rb
@@ -1439,8 +1439,12 @@ module PostHog
 
       expect(FeatureFlagsPoller.match_property(property_a, { 'key' => 'value' })).to be true
       expect(FeatureFlagsPoller.match_property(property_a, { 'key' => 'value2' })).to be true
-      expect(FeatureFlagsPoller.match_property(property_a, { 'key' => '' })).to be true
       expect(FeatureFlagsPoller.match_property(property_a, { 'key' => nil })).to be true
+      expect(FeatureFlagsPoller.match_property(property_a, { 'key' => false })).to be true
+      expect(FeatureFlagsPoller.match_property(property_a, { 'key' => 0 })).to be true
+      expect(FeatureFlagsPoller.match_property(property_a, { 'key' => '' })).to be true
+      expect(FeatureFlagsPoller.match_property(property_a, { 'key' => [] })).to be true
+      expect(FeatureFlagsPoller.match_property(property_a, { 'key' => {} })).to be true
 
       expect do
         FeatureFlagsPoller.match_property(property_a, { 'key2' => 'value' })
@@ -1448,6 +1452,19 @@ module PostHog
       expect { FeatureFlagsPoller.match_property(property_a, {}) }.to raise_error(InconclusiveMatchError)
     end
 
+    it 'with operator is_not_set' do
+      property_a = { 'key' => 'key', 'value' => 'is_not_set', 'operator' => 'is_not_set' }
+
+      expect(FeatureFlagsPoller.match_property(property_a, { 'key' => nil })).to be false
+      expect(FeatureFlagsPoller.match_property(property_a, { 'key' => false })).to be false
+      expect(FeatureFlagsPoller.match_property(property_a, { 'key' => 0 })).to be false
+      expect(FeatureFlagsPoller.match_property(property_a, { 'key' => '' })).to be false
+      expect(FeatureFlagsPoller.match_property(property_a, { 'key' => [] })).to be false
+      expect(FeatureFlagsPoller.match_property(property_a, { 'key' => {} })).to be false
+
+      expect { FeatureFlagsPoller.match_property(property_a, {}) }.to raise_error(InconclusiveMatchError)
+    end
+
     it 'with operator icontains' do
       property_a = { 'key' => 'key', 'value' => 'vaLuE', 'operator' => 'icontains' }