diff --git a/lib/carrierwave/processing/rmagick.rb b/lib/carrierwave/processing/rmagick.rb
index 129fb4de4..39223f124 100644
--- a/lib/carrierwave/processing/rmagick.rb
+++ b/lib/carrierwave/processing/rmagick.rb
@@ -378,9 +378,15 @@ def manipulate!(options={}, &block)
 
     def create_info_block(options)
       return nil unless options
-      assignments = options.map { |k, v| "self.#{k} = #{v}" }
-      code = "lambda { |img| " + assignments.join(";") + "}"
-      eval code
+      proc do |img|
+        options.each do |k, v|
+          if v.is_a?(String) && (matches = v.match(/^["'](.+)["']/))
+            ActiveSupport::Deprecation.warn "Passing quoted strings like #{v} to #manipulate! is deprecated, pass them without quoting."
+            v = matches[1]
+          end
+          img.public_send(:"#{k}=", v)
+        end
+      end
     end
 
     def destroy_image(image)
diff --git a/spec/processing/rmagick_spec.rb b/spec/processing/rmagick_spec.rb
index 2c5d95fde..19037749b 100644
--- a/spec/processing/rmagick_spec.rb
+++ b/spec/processing/rmagick_spec.rb
@@ -208,9 +208,41 @@
 
       instance.manipulate! :read => {
           :density => 10,
-          :size => %{"200x200"}
+          :size => "200x200"
         }
     end
+
+    it 'shows deprecation but still accepts strings enclosed with double quotes' do
+      expect_any_instance_of(::Magick::Image::Info).to receive(:size=).once.with("200x200")
+      expect(ActiveSupport::Deprecation).to receive(:warn).with(any_args)
+      instance.manipulate! :read => {:size => %{"200x200"}}
+    end
+
+    it 'shows deprecation but still accepts strings enclosed with single quotes' do
+      expect_any_instance_of(::Magick::Image::Info).to receive(:size=).once.with("200x200")
+      expect(ActiveSupport::Deprecation).to receive(:warn).with(any_args)
+      instance.manipulate! :read => {:size => %{'200x200'}}
+    end
+
+    it 'does not allow arbitrary code execution' do
+      expect_any_instance_of(Kernel).not_to receive(:puts)
+      expect do
+        instance.manipulate! :read => {
+            :density => "1 }; raise; {"
+        }
+      end.to raise_error ArgumentError, /invalid density geometry/
+    end
+
+    it 'does not allow invocation of non-public methods' do
+      module Kernel
+        private def foo=(value); raise; end
+      end
+      expect do
+        instance.manipulate! :read => {
+            :foo => "1"
+        }
+      end.to raise_error NoMethodError, /private method `foo=' called/
+    end
   end
 
   describe "#width and #height" do