diff --git a/capsicum.gemspec b/capsicum.gemspec
index 0bb485b..7b114bc 100644
--- a/capsicum.gemspec
+++ b/capsicum.gemspec
@@ -33,5 +33,5 @@ Gem::Specification.new do |spec|
   spec.add_development_dependency "rake", "~> 10.0"
   spec.add_development_dependency "minitest", "~> 5.0"
 
-  spec.add_runtime_dependency "ffi", "> 0"
+  spec.add_runtime_dependency "ffi", "~> 1.9"
 end