diff --git a/include/string_span.h b/include/string_span.h
index 786e055..46bf2d4 100644
--- a/include/string_span.h
+++ b/include/string_span.h
@@ -588,16 +588,16 @@ private:
     impl_type span_;
 };
 
-template <size_t Max = dynamic_range>
+template <std::ptrdiff_t Max = dynamic_range>
 using zstring_span = basic_zstring_span<char, Max>;
 
-template <size_t Max = dynamic_range>
+template <std::ptrdiff_t Max = dynamic_range>
 using wzstring_span = basic_zstring_span<wchar_t, Max>;
 
-template <size_t Max = dynamic_range>
+template <std::ptrdiff_t Max = dynamic_range>
 using czstring_span = basic_zstring_span<const char, Max>;
 
-template <size_t Max = dynamic_range>
+template <std::ptrdiff_t Max = dynamic_range>
 using cwzstring_span = basic_zstring_span<const wchar_t, Max>;
 
 } // namespace GSL
diff --git a/tests/string_span_tests.cpp b/tests/string_span_tests.cpp
index 6abdcb9..28d7353 100644
--- a/tests/string_span_tests.cpp
+++ b/tests/string_span_tests.cpp
@@ -846,7 +846,7 @@ SUITE(string_span_tests)
         span[last] = '\0';
 
         auto ret = span.subspan(0, 4);
-        return ret;
+        return{ ret };
     }
 
     TEST(zstring)
@@ -903,7 +903,7 @@ SUITE(string_span_tests)
         span[last] = L'\0';
 
         auto ret = span.subspan(0, 4);
-        return ret;
+        return{ ret };
     }
 
     TEST(wzstring)