diff --git a/src/cpp/ripple/LedgerEntrySet.cpp b/src/cpp/ripple/LedgerEntrySet.cpp
index 7795a4f82..66d9cc5e2 100644
--- a/src/cpp/ripple/LedgerEntrySet.cpp
+++ b/src/cpp/ripple/LedgerEntrySet.cpp
@@ -115,7 +115,7 @@ LedgerEntryAction LedgerEntrySet::hasEntry(const uint256& index) const
 void LedgerEntrySet::entryCache(SLE::ref sle)
 {
 	assert(mLedger);
-	assert(sle->isMutable() || !mImmutable);
+	assert(sle->isMutable() || mImmutable); // Don't put an immutable SLE in a mutable LES
 	std::map<uint256, LedgerEntrySetEntry>::iterator it = mEntries.find(sle->getIndex());
 	if (it == mEntries.end())
 	{