diff --git a/tests/CMakeLists.txt b/tests/CMakeLists.txt
index 3c3125e..2747d3f 100644
--- a/tests/CMakeLists.txt
+++ b/tests/CMakeLists.txt
@@ -24,9 +24,9 @@ else()
     CHECK_CXX_COMPILER_FLAG("-std=c++14" COMPILER_SUPPORTS_CXX14)
     CHECK_CXX_COMPILER_FLAG("-std=c++11" COMPILER_SUPPORTS_CXX11)
     if(COMPILER_SUPPORTS_CXX14)
-    	set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -std=c++14 -Wall -Wno-missing-braces")
+        set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -std=c++14 -O3 -Wall -Wno-missing-braces")
     elseif(COMPILER_SUPPORTS_CXX11)
-    	set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -std=c++11 -Wall -Wno-missing-braces")
+        set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -std=c++11 -O3 -Wall -Wno-missing-braces")
     else()
       message(STATUS "The compiler ${CMAKE_CXX_COMPILER} has no C++11 support. Please use a different C++ compiler.")
     endif()
diff --git a/tests/byte_tests.cpp b/tests/byte_tests.cpp
index 3bbf382..32b0957 100644
--- a/tests/byte_tests.cpp
+++ b/tests/byte_tests.cpp
@@ -43,7 +43,7 @@ SUITE(byte_tests)
             byte b = byte(12);
             CHECK(static_cast<unsigned char>(b) == 12);
         }
-        
+
         {
             byte b = to_byte<12>();
             CHECK(static_cast<unsigned char>(b) == 12);
@@ -61,6 +61,20 @@ SUITE(byte_tests)
         //}
     }
 
+    int modify_both(gsl::byte * b, int* i)
+    {
+        *i = 10;
+        *b = to_byte<5>();
+        return *i;
+    }
+
+    TEST(aliasing)
+    {
+        int i{0};
+        int res = modify_both(reinterpret_cast<byte*>(&i), &i);
+        CHECK(res == i);
+    }
+
     TEST(bitwise_operations)
     {
         byte b = to_byte<0xFF>();