if (length > ucharsPerLoop) {
const size_t endLength = length - ucharsPerLoop + 1;
for (; i < endLength; i += ucharsPerLoop) {
-#ifndef NDEBUG
+#if ENABLE(ASSERT)
for (unsigned checkIndex = 0; checkIndex < ucharsPerLoop; ++checkIndex)
ASSERT(!(source[i+checkIndex] & 0xff00));
#endif