diff --git a/.travis.yml b/.travis.yml
index cb17cef..9171aea 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -10,7 +10,6 @@ gemfile:
   - Gemfile
   - gemfiles/activemodel-3.2.gemfile
   - gemfiles/activemodel-4.2.gemfile
-  - gemfiles/activemodel-5.1.gemfile
   - gemfiles/activemodel-5.2.gemfile
   - gemfiles/activemodel-6.0.gemfile
   - gemfiles/activemodel-master.gemfile
diff --git a/gemfiles/activemodel-5.1.gemfile b/gemfiles/activemodel-5.1.gemfile
deleted file mode 100644
index 8d34236..0000000
--- a/gemfiles/activemodel-5.1.gemfile
+++ /dev/null
@@ -1,5 +0,0 @@
-source "https://rubygems.org"
-
-gem "activemodel", "~> 5.1.0"
-
-gemspec path: "../"
diff --git a/gemfiles/activemodel-6.0.gemfile b/gemfiles/activemodel-6.0.gemfile
index b7bd17e..dfdf34a 100644
--- a/gemfiles/activemodel-6.0.gemfile
+++ b/gemfiles/activemodel-6.0.gemfile
@@ -1,5 +1,5 @@
 source "https://rubygems.org"
 
-gem "activemodel", ">= 6.0.0.beta1", "< 7.0"
+gem "activemodel", "~> 6.0.0"
 
 gemspec path: "../"
diff --git a/lib/strip_attributes.rb b/lib/strip_attributes.rb
index 63aef50..13db4ed 100644
--- a/lib/strip_attributes.rb
+++ b/lib/strip_attributes.rb
@@ -9,13 +9,6 @@ def strip_attributes(options = {})
       StripAttributes.strip(record, options)
     end
   end
-
-  # <b>DEPRECATED:</b> Please use <tt>strip_attributes</tt> (non-bang method)
-  # instead.
-  def strip_attributes!(options = {})
-    warn "[DEPRECATION] `strip_attributes!` is deprecated. Please use `strip_attributes` (non-bang method) instead."
-    strip_attributes(options)
-  end
 end
 
 module StripAttributes