diff --git a/include/internal/catch_test_case_registry_impl.hpp b/include/internal/catch_test_case_registry_impl.hpp
index 04bd37fc..a70b019b 100644
--- a/include/internal/catch_test_case_registry_impl.hpp
+++ b/include/internal/catch_test_case_registry_impl.hpp
@@ -24,9 +24,9 @@
 #endif
 
 namespace Catch {
-    
+
     struct RandomNumberGenerator {
-        typedef int result_type;
+        typedef std::ptrdiff_t result_type;
 
         result_type operator()( result_type n ) const { return std::rand() % n; }