diff --git a/.gitmodules b/.gitmodules
index da6957d..6b07f5f 100644
--- a/.gitmodules
+++ b/.gitmodules
@@ -1,4 +1,4 @@
 [submodule "spec/engine-test-data"]
 	path = spec/engine-test-data
 	url = git@github.com:Flagsmith/engine-test-data.git
-	branch = main
+	branch = v3.5.0
diff --git a/Gemfile.lock b/Gemfile.lock
index 249a91e..b1643c7 100644
--- a/Gemfile.lock
+++ b/Gemfile.lock
@@ -73,7 +73,7 @@ GEM
     ruby-progressbar (1.13.0)
     semantic (1.6.1)
     unicode-display_width (2.5.0)
-    uri (0.13.2)
+    uri (1.1.1)
 
 PLATFORMS
   ruby
diff --git a/lib/flagsmith/engine/segments/evaluator.rb b/lib/flagsmith/engine/segments/evaluator.rb
index c5d55cb..a9402f3 100644
--- a/lib/flagsmith/engine/segments/evaluator.rb
+++ b/lib/flagsmith/engine/segments/evaluator.rb
@@ -157,8 +157,18 @@ def traits_match_segment_condition_from_context(condition, segment_key, context)
         end
 
         def handle_percentage_split(condition, segment_key, context)
-          context_value_key = get_context_value(condition[:property], context) || get_identity_key_from_context(context)
-          hashed_percentage = hashed_percentage_for_object_ids([segment_key, context_value_key])
+          split_key = if condition[:property].nil? || condition[:property].empty?
+                        # No property specified - use identity key
+                        get_identity_key_from_context(context)
+                      else
+                        # Property specified - must exist in context
+                        get_context_value(condition[:property], context)
+                      end
+
+          # If split_key is nil, condition doesn't match
+          return false if split_key.nil?
+
+          hashed_percentage = hashed_percentage_for_object_ids([segment_key, split_key])
           hashed_percentage <= condition[:value].to_f
         end
 
diff --git a/spec/engine-test-data b/spec/engine-test-data
index 839e8d5..7840a13 160000
--- a/spec/engine-test-data
+++ b/spec/engine-test-data
@@ -1 +1 @@
-Subproject commit 839e8d5e5f2e9af6392062cf5e575d43c03770d4
+Subproject commit 7840a1349b601df3b6b4a089f40864f659801afb