diff --git a/lib/paperclip/attachment.rb b/lib/paperclip/attachment.rb
index 65c26ddc7..f2e7d672a 100644
--- a/lib/paperclip/attachment.rb
+++ b/lib/paperclip/attachment.rb
@@ -109,8 +109,6 @@ def assign(uploaded_file)
           nil
         else
           assign_attributes
-          post_process_file
-          reset_file_if_original_reprocessed
         end
       else
         nil
@@ -238,6 +236,8 @@ def dirty?
     # Saves the file, if there are no errors. If there are, it flushes them to
     # the instance's errors and returns false, cancelling the save.
     def save
+      post_process_file
+      reset_file_if_original_reprocessed
       flush_deletes unless @options[:keep_old_files]
       process = only_process
       if process.any? && !process.include?(:original)
diff --git a/spec/paperclip/attachment_processing_spec.rb b/spec/paperclip/attachment_processing_spec.rb
index f0231440f..e90c0c0f3 100644
--- a/spec/paperclip/attachment_processing_spec.rb
+++ b/spec/paperclip/attachment_processing_spec.rb
@@ -4,34 +4,47 @@
   before { rebuild_class }
 
   context 'using validates_attachment_content_type' do
-    it 'processes attachments given a valid assignment' do
+    it "doesn't process attachments on assignment" do
       file = File.new(fixture_file("5k.png"))
       Dummy.validates_attachment_content_type :avatar, content_type: "image/png"
       instance = Dummy.new
       attachment = instance.avatar
-      attachment.expects(:post_process_styles)
+      attachment.expects(:post_process_styles).never
 
       attachment.assign(file)
     end
 
-    it 'does not process attachments given an invalid assignment with :not' do
+    it 'processes attachments given the object is valid' do
+      file = File.new(fixture_file("5k.png"))
+      Dummy.validates_attachment_content_type :avatar, content_type: "image/png"
+      instance = Dummy.new
+      attachment = instance.avatar
+      attachment.assign(file)
+      attachment.expects(:post_process_styles)
+
+      attachment.save
+    end
+
+    it 'does not process attachments given an invalid object with :not' do
       file = File.new(fixture_file("5k.png"))
       Dummy.validates_attachment_content_type :avatar, not: "image/png"
       instance = Dummy.new
       attachment = instance.avatar
+      attachment.assign(file)
       attachment.expects(:post_process_styles).never
 
-      attachment.assign(file)
+      attachment.save
     end
 
-    it 'does not process attachments given an invalid assignment with :content_type' do
+    it 'does not process attachments given an invalid object with :content_type' do
       file = File.new(fixture_file("5k.png"))
       Dummy.validates_attachment_content_type :avatar, content_type: "image/tiff"
       instance = Dummy.new
       attachment = instance.avatar
+      attachment.assign(file)
       attachment.expects(:post_process_styles).never
 
-      attachment.assign(file)
+      attachment.save
     end
 
     it 'allows what would be an invalid assignment when validation :if clause returns false' do
@@ -39,14 +52,15 @@
       Dummy.validates_attachment_content_type :avatar, content_type: "image/tiff", if: lambda{false}
       instance = Dummy.new
       attachment = instance.avatar
+      attachment.assign(invalid_assignment)
       attachment.expects(:post_process_styles)
 
-      attachment.assign(invalid_assignment)
+      attachment.save
     end
   end
 
   context 'using validates_attachment' do
-    it 'processes attachments given a valid assignment' do
+    it "doesn't process attachments on assignment" do
       file = File.new(fixture_file("5k.png"))
       Dummy.validates_attachment :avatar, content_type: {content_type: "image/png"}
       instance = Dummy.new
@@ -56,24 +70,37 @@
       attachment.assign(file)
     end
 
-    it 'does not process attachments given an invalid assignment with :not' do
+    it 'processes attachments given a valid object' do
+      file = File.new(fixture_file("5k.png"))
+      Dummy.validates_attachment :avatar, content_type: {content_type: "image/png"}
+      instance = Dummy.new
+      attachment = instance.avatar
+      attachment.assign(file)
+      attachment.expects(:post_process_styles)
+
+      attachment.save
+    end
+
+    it 'does not process attachments given an invalid object with :not' do
       file = File.new(fixture_file("5k.png"))
       Dummy.validates_attachment :avatar, content_type: {not: "image/png"}
       instance = Dummy.new
       attachment = instance.avatar
+      attachment.assign(file)
       attachment.expects(:post_process_styles).never
 
-      attachment.assign(file)
+      attachment.save
     end
 
-    it 'does not process attachments given an invalid assignment with :content_type' do
+    it 'does not process attachments given an invalid object with :content_type' do
       file = File.new(fixture_file("5k.png"))
       Dummy.validates_attachment :avatar, content_type: {content_type: "image/tiff"}
       instance = Dummy.new
       attachment = instance.avatar
+      attachment.assign(file)
       attachment.expects(:post_process_styles).never
 
-      attachment.assign(file)
+      attachment.save
     end
   end
 end
diff --git a/spec/paperclip/attachment_spec.rb b/spec/paperclip/attachment_spec.rb
index 76d7e9fb4..d766e7162 100644
--- a/spec/paperclip/attachment_spec.rb
+++ b/spec/paperclip/attachment_spec.rb
@@ -711,9 +711,10 @@ class Paperclip::Test < Paperclip::Processor; end
       Paperclip::Thumbnail.stubs(:make).returns(@file)
     end
 
-    context "when assigned" do
+    context "when saved" do
       it "calls #make on all specified processors" do
         @dummy.avatar = @file
+        @dummy.save
 
         expect(Paperclip::Thumbnail).to have_received(:make)
         expect(Paperclip::Test).to have_received(:make)
@@ -729,12 +730,14 @@ class Paperclip::Test < Paperclip::Processor; end
         })
 
         @dummy.avatar = @file
+        @dummy.save
 
         expect(Paperclip::Thumbnail).to have_received(:make).with(anything, expected_params, anything)
       end
 
       it "calls #make with attachment passed as third argument" do
         @dummy.avatar = @file
+        @dummy.save
 
         expect(Paperclip::Test).to have_received(:make).with(anything, anything, @dummy.avatar)
       end
@@ -745,6 +748,42 @@ class Paperclip::Test < Paperclip::Processor; end
         @dummy.avatar = @file
       end
     end
+
+    context "when assigned" do
+      it "doesn't call #make on all specified processors" do
+        @dummy.avatar = @file
+
+        expect(Paperclip::Thumbnail).not_to have_received(:make)
+        expect(Paperclip::Test).not_to have_received(:make)
+      end
+
+      it "doesn't call #make with the right parameters passed as second argument" do
+        expected_params = @style_params[:once].merge({
+          style: :once,
+          processors: [:thumbnail, :test],
+          whiny: true,
+          convert_options: "",
+          source_file_options: ""
+        })
+
+        @dummy.avatar = @file
+
+        expect(Paperclip::Thumbnail).not_to have_received(:make).with(anything, expected_params, anything)
+      end
+
+      it "doesn't call #make with attachment passed as third argument" do
+        @dummy.avatar = @file
+
+        expect(Paperclip::Test).not_to have_received(:make).with(anything, anything, @dummy.avatar)
+      end
+
+      it "doesn't call #make and unlinks intermediary files afterward" do
+        # TODO: Fix this test?
+        @dummy.avatar.expects(:unlink_files).with([@file, @file])
+
+        @dummy.avatar = @file
+      end
+    end
   end
 
   context "An attachment with a processor that returns original file" do
@@ -758,8 +797,18 @@ def make; @file; end
       @dummy = Dummy.new
     end
 
+    context "when saved" do
+      it "calls #make and doesn't unlink the original file" do
+        @dummy.avatar.expects(:unlink_files).with([])
+
+        @dummy.avatar = @file
+        @dummy.save
+      end
+    end
+
     context "when assigned" do
-      it "#calls #make and doesn't unlink the original file" do
+      it "doesn't call #make and doesn't unlink the original file" do
+        # TODO: Fix this test?
         @dummy.avatar.expects(:unlink_files).with([])
 
         @dummy.avatar = @file
@@ -822,6 +871,7 @@ def make; @file; end
   end
 
   context "Assigning an attachment with post_process hooks" do
+    # NOTE: Investigate the before_post_process hooks, as they may be intended to run on assignment
     before do
       rebuild_class styles: { something: "100x100#" }
       Dummy.class_eval do
@@ -841,13 +891,23 @@ def do_after_all; end
       @attachment = @dummy.avatar
     end
 
-    it "calls the defined callbacks when assigned" do
+    it "calls the defined callbacks when saved" do
       @dummy.expects(:do_before_avatar).with()
       @dummy.expects(:do_after_avatar).with()
       @dummy.expects(:do_before_all).with()
       @dummy.expects(:do_after_all).with()
       Paperclip::Thumbnail.expects(:make).returns(@file)
       @dummy.avatar = @file
+      @dummy.save
+    end
+
+    it "doesn't call the defined callbacks when assigned" do
+      @dummy.expects(:do_before_avatar).never
+      @dummy.expects(:do_after_avatar).never
+      @dummy.expects(:do_before_all).never
+      @dummy.expects(:do_after_all).never
+      Paperclip::Thumbnail.expects(:make).never
+      @dummy.avatar = @file
     end
 
     it "does not cancel the processing if a before_post_process returns nil" do
@@ -857,6 +917,7 @@ def do_after_all; end
       @dummy.expects(:do_after_all).with()
       Paperclip::Thumbnail.expects(:make).returns(@file)
       @dummy.avatar = @file
+      @dummy.save
     end
 
     it "cancels the processing if a before_post_process returns false" do
@@ -866,6 +927,7 @@ def do_after_all; end
       @dummy.expects(:do_after_all)
       Paperclip::Thumbnail.expects(:make).never
       @dummy.avatar = @file
+      @dummy.save
     end
 
     it "cancels the processing if a before_avatar_post_process returns false" do
@@ -875,6 +937,7 @@ def do_after_all; end
       @dummy.expects(:do_after_all)
       Paperclip::Thumbnail.expects(:make).never
       @dummy.avatar = @file
+      @dummy.save
     end
   end