diff --git a/include/mbedtls/config.h b/include/mbedtls/config.h
index e00c546..124c597 100644
--- a/include/mbedtls/config.h
+++ b/include/mbedtls/config.h
@@ -1907,6 +1907,19 @@
 //#define MBEDTLS_SSL_VARIABLE_BUFFER_LENGTH
 
 /**
+ * \def MBEDTLS_TEST_CONSTANT_FLOW_MEMSAN
+ *
+ * Enable testing of the constant-flow nature of some sensitive functions with
+ * clang's MemorySanitizer. This causes some existing tests to also test
+ * non-functional properties of the code under test.
+ *
+ * This setting requires compiling with clang -fsanitize=memory.
+ *
+ * Uncomment to enable testing of the constant-flow nature of seletected code.
+ */
+//#define MBEDTLS_TEST_CONSTANT_FLOW_MEMSAN
+
+/**
  * \def MBEDTLS_TEST_HOOKS
  *
  * Enable features for invasive testing such as introspection functions and