diff --git a/.travis.yml b/.travis.yml
index b75754d8..300066f9 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -1,9 +1,15 @@
 language: ruby
 
-before_install:
-  - gem install bundler
-
-rvm:
-- 1.9.3
-- ruby-head
+matrix:
+  include:
+    - name: "Ruby 1.9"
+      dist: precise
+      rvm: 1.9.3
+      before_install:
+        - gem install bundler -v 1.17.3
+    - name: "Ruby 2.5.3"
+      dist: xenial
+      rvm: ruby-2.5.3
+      before_install:
+        - gem install bundler
 script: bundle exec rspec
diff --git a/cloudinary.gemspec b/cloudinary.gemspec
index 66d7b748..431bd4de 100644
--- a/cloudinary.gemspec
+++ b/cloudinary.gemspec
@@ -28,6 +28,6 @@ Gem::Specification.new do |s|
   s.add_development_dependency "rake"
   s.add_development_dependency "rspec", '>=3.5'
   s.add_development_dependency "rspec-rails"
-  s.add_development_dependency "rubyzip", "<=1.2.0" # support testing Ruby 1.9
+  s.add_development_dependency "rubyzip", ">= 1.2.2" # support testing Ruby 1.9
   s.add_development_dependency "simplecov"
 end
diff --git a/lib/cloudinary/utils.rb b/lib/cloudinary/utils.rb
index 353e495e..d050e49c 100644
--- a/lib/cloudinary/utils.rb
+++ b/lib/cloudinary/utils.rb
@@ -305,7 +305,7 @@ def self.process_if(ifValue)
   EXP_REPLACEMENT = PREDEFINED_VARS.merge(CONDITIONAL_OPERATORS)
 
   def self.normalize_expression(expression)
-    if expression =~ /^!.+!$/ # quoted string
+    if expression.is_a?( String) && expression =~ /^!.+!$/ # quoted string
       expression
     else
       expression.to_s.gsub(EXP_REGEXP,EXP_REPLACEMENT).gsub(/[ _]+/, "_")