diff --git a/m-core.h b/m-core.h
index ecc6c0bf..770957d0 100644
--- a/m-core.h
+++ b/m-core.h
@@ -279,6 +279,16 @@ M_BEGIN_PROTECTED_CODE
 #endif
 
 
+/* If within the M*LIB tests, perform additional (potentialy slow) checks */
+#ifndef M_ASSERT_SLOW
+# if defined(M_USE_ADDITIONAL_CHECKS) && M_USE_ADDITIONAL_CHECKS
+#  define M_ASSERT_SLOW(n) assert(n)
+# else
+#  define M_ASSERT_SLOW(n) (void) 0
+# endif
+#endif
+
+
 /* Always perform a runtime check of the given condition
  * NOTE: Can be overiden by user if it needs to keep finer access 
  * on the assertions or display message on another device.
diff --git a/m-serial-bin.h b/m-serial-bin.h
index a79bd4cc..0bd0e6cf 100644
--- a/m-serial-bin.h
+++ b/m-serial-bin.h
@@ -181,7 +181,7 @@ m_serial_bin_write_float(m_serial_write_t serial, const long double data, const
 static inline m_serial_return_code_t
 m_serial_bin_write_string(m_serial_write_t serial, const char data[], size_t length)
 {
-  STRINGI_ASSERT_SLOW(length == strlen(data) );
+  M_ASSERT_SLOW(length == strlen(data) );
   FILE *f = (FILE *)serial->data[0].p;
   M_ASSERT(f != NULL && data != NULL);
   // Write first the number of (non null) characters
diff --git a/m-serial-json.h b/m-serial-json.h
index 26d212ea..a1045881 100644
--- a/m-serial-json.h
+++ b/m-serial-json.h
@@ -67,7 +67,7 @@ m_serial_json_write_float(m_serial_write_t serial, const long double data, const
 static inline m_serial_return_code_t
 m_serial_json_write_string(m_serial_write_t serial, const char data[], size_t length)
 {
-  STRINGI_ASSERT_SLOW(length == strlen(data) );
+  M_ASSERT_SLOW(length == strlen(data) );
   FILE *f = (FILE *)serial->data[0].p;
   M_ASSERT(f != NULL && data != NULL);
   /* HACK: Build dummy string to reuse string_out_str */
diff --git a/m-string.h b/m-string.h
index 463c0ade..d76a08b8 100644
--- a/m-string.h
+++ b/m-string.h
@@ -37,19 +37,12 @@ M_BEGIN_PROTECTED_CODE
 
 /********************************** INTERNAL ************************************/
 
-/* If within the string tests, perform additional (potentialy slow) checks */
-#ifdef STRING_WITHIN_TEST
-# define STRINGI_ASSERT_SLOW(n) M_ASSERT(n)
-#else
-# define STRINGI_ASSERT_SLOW(n) (void) 0
-#endif
-
 // This macro defines the contract of a string.
 // Note: A ==> B is represented as not(A) or B
 // Note: use of strlen can slow down a lot the program in some cases.
 #define STRINGI_CONTRACT(v) do {                                              \
     M_ASSERT (v != NULL);                                                     \
-    STRINGI_ASSERT_SLOW (string_size(v) == strlen(string_get_cstr(v)));       \
+    M_ASSERT_SLOW (string_size(v) == strlen(string_get_cstr(v)));             \
     M_ASSERT (string_get_cstr(v)[string_size(v)] == 0);                       \
     M_ASSERT (string_size(v) < string_capacity(v));                           \
     M_ASSERT (string_capacity(v) < sizeof (string_heap_ct) || !stringi_stack_p(v)); \
diff --git a/tests/test-mstring.c b/tests/test-mstring.c
index 1d2dd4f1..502ca4df 100644
--- a/tests/test-mstring.c
+++ b/tests/test-mstring.c
@@ -21,7 +21,7 @@
  * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */
 
-#define STRING_WITHIN_TEST
+#define M_USE_ADDITIONAL_CHECKS 1
 #include "m-string.h"
 
 BOUNDED_STRING_DEF(string16, 16)