diff --git a/lib/roo/helpers/weak_instance_cache.rb b/lib/roo/helpers/weak_instance_cache.rb
index bc853877..db26de1a 100644
--- a/lib/roo/helpers/weak_instance_cache.rb
+++ b/lib/roo/helpers/weak_instance_cache.rb
@@ -30,8 +30,8 @@ def instance_cache(key)
       end
 
       def instance_cache_finalizer(key)
-        proc do
-          if instance_variable_defined?(key) && (ref = instance_variable_get(key)) && !ref.weakref_alive?
+        proc do |object_id|
+          if instance_variable_defined?(key) && (ref = instance_variable_get(key)) && (!ref.weakref_alive? || ref.__getobj__.object_id == object_id)
             remove_instance_variable(key)
           end
         end
diff --git a/spec/lib/roo/weak_instance_cache_spec.rb b/spec/lib/roo/weak_instance_cache_spec.rb
index cc2caf46..5adcb908 100644
--- a/spec/lib/roo/weak_instance_cache_spec.rb
+++ b/spec/lib/roo/weak_instance_cache_spec.rb
@@ -1,5 +1,10 @@
 require 'spec_helper'
 
+if RUBY_PLATFORM == "java"
+  require 'java'
+  java_import 'java.lang.System'
+end
+
 describe Roo::Helpers::WeakInstanceCache do
   let(:klass) do
     Class.new do
@@ -7,7 +12,7 @@
 
       def memoized_data
         instance_cache(:@memoized_data) do
-          "Some Costly Operation" * 1_000
+          "Some Costly Operation #{rand(1000)}" * 1_000
         end
       end
     end
@@ -30,21 +35,25 @@ def memoized_data
   end
 
   it 'should recalculate after GC' do
+    expect(subject.instance_variables).to_not include(:@memoized_data)
     GC.disable
-    original_id = subject.memoized_data.object_id
-    expect(subject.memoized_data.object_id).to eq(original_id)
+    subject.memoized_data && nil
+    expect(subject.instance_variables).to include(:@memoized_data)
 
-    GC.start
-    expect(subject.memoized_data.object_id).not_to eq(original_id)
+    force_gc
+    expect(subject.instance_variables).to_not include(:@memoized_data)
+    GC.disable
+    subject.memoized_data && nil
+    expect(subject.instance_variables).to include(:@memoized_data)
   end
 
   it 'must remove instance variable' do
     expect(subject.instance_variables).to_not include(:@memoized_data)
     GC.disable
-    subject.memoized_data
+    subject.memoized_data && nil
     expect(subject.instance_variables).to include(:@memoized_data)
 
-    GC.start
+    force_gc
     expect(subject.instance_variables).to_not include(:@memoized_data)
   end
 
@@ -54,16 +63,28 @@ def memoized_data
     end
     it 'after calculation' do
       GC.disable
-      subject.memoized_data
+      subject.memoized_data && nil
       expect{subject.inspect}.to_not raise_error
       expect(subject.inspect).to include("Some Costly Operation")
-      GC.start
+      force_gc
     end
     it 'after GC' do
-      subject.memoized_data
-      GC.start
+      subject.memoized_data && nil
+      force_gc
+      expect(subject.instance_variables).to_not include(:@memoized_data)
       expect{subject.inspect}.to_not raise_error
       expect(subject.inspect).to_not include("Some Costly Operation")
     end
   end
+
+  if RUBY_PLATFORM == "java"
+    def force_gc
+      System.gc
+      sleep(0.1)
+    end
+  else
+    def force_gc
+      GC.start
+    end
+  end
 end
\ No newline at end of file