diff --git a/include/stdex/html.hpp b/include/stdex/html.hpp
index 7105cb0cb..4f21ccc5e 100644
--- a/include/stdex/html.hpp
+++ b/include/stdex/html.hpp
@@ -1440,7 +1440,7 @@ namespace stdex
 					{ "wbr",        element_t::wbr,        },
 					{ "xmp",        element_t::xmp,        },
 				};
-#ifdef _DEBUG
+#ifndef NDEBUG
 				// The mapping table MUST be sorted and all names in lowercase.
 				for (size_t i = 1; i < _countof(mapping); i++)
 					_Assume_(stdex::strcmp(mapping[i - 1].name, mapping[i].name) <= 0);
diff --git a/include/stdex/ring.hpp b/include/stdex/ring.hpp
index 795a86209..87746e270 100644
--- a/include/stdex/ring.hpp
+++ b/include/stdex/ring.hpp
@@ -55,7 +55,7 @@ namespace stdex
 		{
 			{
 				const std::lock_guard<std::mutex> lg(m_mutex);
-#ifdef _DEBUG
+#ifndef NDEBUG
 				size_t tail = wrap(m_head + m_size);
 				_Assume_(size <= (m_head <= tail ? N_cap - tail : m_head - tail));
 #endif
@@ -90,7 +90,7 @@ namespace stdex
 		{
 			{
 				const std::lock_guard<std::mutex> lg(m_mutex);
-#ifdef _DEBUG
+#ifndef NDEBUG
 				size_t tail = wrap(m_head + m_size);
 				_Assume_(size <= (m_head < tail ? m_size : N_cap - m_head));
 #endif