diff --git a/lib/ransack/adapters/active_record/base.rb b/lib/ransack/adapters/active_record/base.rb
index 75383f1..6bdb8fb 100644
--- a/lib/ransack/adapters/active_record/base.rb
+++ b/lib/ransack/adapters/active_record/base.rb
@@ -12,9 +12,7 @@ module Ransack
         end
 
         def ransack(params = {}, options = {})
-          params = params.presence || {}
-          Search.new(self, params ? params.delete_if {
-            |k, v| v.blank? && v != false } : params, options)
+          Search.new(self, params, options)
         end
 
         def ransacker(name, opts = {}, &block)
diff --git a/lib/ransack/search.rb b/lib/ransack/search.rb
index e8e5a76..bd99fce 100644
--- a/lib/ransack/search.rb
+++ b/lib/ransack/search.rb
@@ -14,9 +14,12 @@ module Ransack
              :translate, :to => :base
 
     def initialize(object, params = {}, options = {})
-      params = {} unless params.is_a?(Hash)
-      (params ||= {})
-      .delete_if { |k, v| [*v].all? { |i| i.blank? && i != false } }
+      if params.is_a? Hash
+        params = params.dup
+        params.delete_if { |k, v| [*v].all?{|i| i.blank? && i != false } }
+      else
+        params = {}
+      end
       @context = options[:context] || Context.for(object, options)
       @context.auth_object = options[:auth_object]
       @base = Nodes::Grouping.new(@context, options[:grouping] || 'and')
diff --git a/spec/ransack/adapters/active_record/base_spec.rb b/spec/ransack/adapters/active_record/base_spec.rb
index 551cf3c..789e5a8 100644
--- a/spec/ransack/adapters/active_record/base_spec.rb
+++ b/spec/ransack/adapters/active_record/base_spec.rb
@@ -50,6 +50,14 @@ module Ransack
             end
           end
 
+          it 'does not raise exception for string :params argument' do
+            lambda { Person.search('') }.should_not raise_error
+          end
+
+          it 'does not modify the parameters' do
+            params = { :name_eq => '' }
+            expect { Person.search(params)}.not_to change { params }
+          end
         end
 
         describe '#ransacker' do
diff --git a/spec/ransack/search_spec.rb b/spec/ransack/search_spec.rb
index 2a810a0..c443a1f 100644
--- a/spec/ransack/search_spec.rb
+++ b/spec/ransack/search_spec.rb
@@ -183,6 +183,12 @@ module Ransack
           specify { expect { subject }.not_to raise_error }
         end
       end
+
+      it 'does not modify the parameters' do
+        params = { :name_eq => '' }
+        expect { Search.new(Person, params)}.not_to change { params }
+      end
+
     end
 
     describe '#result' do