diff --git a/build.gradle b/build.gradle
index fd28b9984..00514ff38 100644
--- a/build.gradle
+++ b/build.gradle
@@ -307,7 +307,7 @@ tasks.register("installBundler") {
     dependsOn assemblyDeps
     outputs.files file("${projectDir}/vendor/bundle/jruby/2.5.0/bin/bundle")
     doLast {
-      gem(projectDir, buildDir, "bundler", "= 2.3.6", "${projectDir}/vendor/bundle/jruby/2.5.0")
+      gem(projectDir, buildDir, "bundler", "~> 2", "${projectDir}/vendor/bundle/jruby/2.5.0")
   }
 }
 
@@ -435,7 +435,7 @@ tasks.register("installIntegrationTestBundler"){
     dependsOn unpackTarDistribution
     outputs.files file("${qaBundleBin}")
   doLast {
-      gem(projectDir, buildDir, "bundler", "= 2.3.6", qaBundledGemPath)
+      gem(projectDir, buildDir, "bundler", "~> 2", qaBundledGemPath)
   }
 }
 
diff --git a/spec/support/pack/valid-pack/logstash/valid-pack/logstash-input-packtest.gemspec b/spec/support/pack/valid-pack/logstash/valid-pack/logstash-input-packtest.gemspec
index 78a7a1d48..49d8922c0 100644
--- a/spec/support/pack/valid-pack/logstash/valid-pack/logstash-input-packtest.gemspec
+++ b/spec/support/pack/valid-pack/logstash/valid-pack/logstash-input-packtest.gemspec
@@ -4,7 +4,6 @@ Gem::Specification.new do |spec|
   spec.version       = "0.0.1"
   spec.authors       = ["Elastic"]
   spec.email         = ["info@elastic.co"]
-
   spec.summary       = "a summary"
   spec.description   = "a description"
   spec.homepage      = "https://elastic.co"
diff --git a/spec/support/pack/valid-pack/logstash/valid-pack/logstash-input-packtest_pim-0.0.1.gem b/spec/support/pack/valid-pack/logstash/valid-pack/logstash-input-packtest_pim-0.0.1.gem
new file mode 100644
index 000000000..a7ecc37be
Binary files /dev/null and b/spec/support/pack/valid-pack/logstash/valid-pack/logstash-input-packtest_pim-0.0.1.gem differ
diff --git a/spec/support/pack/valid-pack/logstash/valid-pack/logstash-input-packtest_pim.gemspec b/spec/support/pack/valid-pack/logstash/valid-pack/logstash-input-packtest_pim.gemspec
new file mode 100644
index 000000000..fbb1c92cb
--- /dev/null
+++ b/spec/support/pack/valid-pack/logstash/valid-pack/logstash-input-packtest_pim.gemspec
@@ -0,0 +1,12 @@
+# coding: utf-8
+Gem::Specification.new do |spec|
+  spec.name                 = "logstash-input-packtest_pim"
+  spec.version              = "0.0.1"
+  spec.authors              = ["Elastic"]
+  spec.email                = ["info@elastic.co"]
+  spec.post_install_message = "Hello from the friendly pack"
+  spec.summary              = "a summary"
+  spec.description          = "a description"
+  spec.homepage             = "https://elastic.co"
+  spec.add_runtime_dependency "logstash-input-packtestdep"
+end
diff --git a/spec/unit/plugin_manager/gem_installer_spec.rb b/spec/unit/plugin_manager/gem_installer_spec.rb
index cf57c9c4a..dd85009df 100644
--- a/spec/unit/plugin_manager/gem_installer_spec.rb
+++ b/spec/unit/plugin_manager/gem_installer_spec.rb
@@ -46,9 +46,7 @@ describe LogStash::PluginManager::GemInstaller do
     let(:message) { "Hello from the friendly pack" }
 
     context "when present" do
-      before do
-        allow_any_instance_of(::Gem::Specification).to receive(:post_install_message).and_return(message)
-      end
+      let(:plugin_name) { 'logstash-input-packtest_pim-0.0.1' }
 
       context "when we want the message" do
         it "display the message" do
@@ -64,7 +62,7 @@ describe LogStash::PluginManager::GemInstaller do
     end
 
     context "when not present" do
-      context "when we want the message" do
+      context "when we don't want the message" do
         it "doesn't display the message" do
           expect(LogStash::PluginManager.ui).not_to receive(:info).with(message)
           subject.install(simple_gem, true, temporary_gem_home)
diff --git a/spec/unit/plugin_manager/pack_installer/pack_spec.rb b/spec/unit/plugin_manager/pack_installer/pack_spec.rb
index 617c0adc0..5467dd2f8 100644
--- a/spec/unit/plugin_manager/pack_installer/pack_spec.rb
+++ b/spec/unit/plugin_manager/pack_installer/pack_spec.rb
@@ -29,8 +29,8 @@ describe LogStash::PluginManager::PackInstaller::Pack do
     end
 
     it "returns the plugins" do
-      expect(subject.plugins.size).to eq(1)
-      expect(subject.plugins.collect(&:name)).to include("logstash-input-packtest")
+      expect(subject.plugins.size).to eq(2)
+      expect(subject.plugins.collect(&:name)).to include("logstash-input-packtest_pim", "logstash-input-packtest")
     end
 
     it "returns the dependencies" do
@@ -39,8 +39,8 @@ describe LogStash::PluginManager::PackInstaller::Pack do
     end
 
     it "returns all the gems" do
-      expect(subject.gems.size).to eq(2)
-      expect(subject.gems.collect(&:name)).to include("logstash-input-packtest", "logstash-input-packtestdep")
+      expect(subject.gems.size).to eq(3)
+      expect(subject.gems.collect(&:name)).to include("logstash-input-packtest", "logstash-input-packtest_pim", "logstash-input-packtestdep")
     end
   end