diff --git a/src/init.cpp b/src/init.cpp
index f0334a08e..eb191ab7b 100644
--- a/src/init.cpp
+++ b/src/init.cpp
@@ -1340,10 +1340,11 @@ bool AppInitMain(boost::thread_group& threadGroup, CScheduler& scheduler)
     nCoinDBCache = std::min(nCoinDBCache, nMaxCoinsDBCache << 20); // cap total coins db cache
     nTotalCache -= nCoinDBCache;
     nCoinCacheUsage = nTotalCache; // the rest goes to in-memory cache
+    int64_t nMempoolSizeMax = GetArg("-maxmempool", DEFAULT_MAX_MEMPOOL_SIZE) * 1000000;
     LogPrintf("Cache configuration:\n");
     LogPrintf("* Using %.1fMiB for block index database\n", nBlockTreeDBCache * (1.0 / 1024 / 1024));
     LogPrintf("* Using %.1fMiB for chain state database\n", nCoinDBCache * (1.0 / 1024 / 1024));
-    LogPrintf("* Using %.1fMiB for in-memory UTXO set\n", nCoinCacheUsage * (1.0 / 1024 / 1024));
+    LogPrintf("* Using %.1fMiB for in-memory UTXO set (plus up to %.1fMiB of unused mempool space)\n", nCoinCacheUsage * (1.0 / 1024 / 1024), nMempoolSizeMax * (1.0 / 1024 / 1024));
 
     bool fLoaded = false;
     while (!fLoaded) {
diff --git a/src/validation.cpp b/src/validation.cpp
index ca1e5a713..f5f685112 100644
--- a/src/validation.cpp
+++ b/src/validation.cpp
@@ -1917,6 +1917,7 @@ bool ConnectBlock(const CBlock& block, CValidationState& state, CBlockIndex* pin
  * or always and in all cases if we're in prune mode and are deleting files.
  */
 bool static FlushStateToDisk(CValidationState &state, FlushStateMode mode) {
+    int64_t nMempoolUsage = mempool.DynamicMemoryUsage();
     const CChainParams& chainparams = Params();
     LOCK2(cs_main, cs_LastBlockFile);
     static int64_t nLastWrite = 0;
@@ -1947,11 +1948,13 @@ bool static FlushStateToDisk(CValidationState &state, FlushStateMode mode) {
     if (nLastSetChain == 0) {
         nLastSetChain = nNow;
     }
-    size_t cacheSize = pcoinsTip->DynamicMemoryUsage();
-    // The cache is large and close to the limit, but we have time now (not in the middle of a block processing).
-    bool fCacheLarge = mode == FLUSH_STATE_PERIODIC && cacheSize * (10.0/9) > nCoinCacheUsage;
+    int64_t nMempoolSizeMax = GetArg("-maxmempool", DEFAULT_MAX_MEMPOOL_SIZE) * 1000000;
+    int64_t cacheSize = pcoinsTip->DynamicMemoryUsage();
+    int64_t nTotalSpace = nCoinCacheUsage + std::max<int64_t>(nMempoolSizeMax - nMempoolUsage, 0);
+    // The cache is large and we're within 10% and 100 MiB of the limit, but we have time now (not in the middle of a block processing).
+    bool fCacheLarge = mode == FLUSH_STATE_PERIODIC && cacheSize > std::max((9 * nTotalSpace) / 10, nTotalSpace - 100 * 1024 * 1024);
     // The cache is over the limit, we have to write now.
-    bool fCacheCritical = mode == FLUSH_STATE_IF_NEEDED && cacheSize > nCoinCacheUsage;
+    bool fCacheCritical = mode == FLUSH_STATE_IF_NEEDED && cacheSize > nTotalSpace;
     // It's been a while since we wrote the block index to disk. Do this frequently, so we don't need to redownload after a crash.
     bool fPeriodicWrite = mode == FLUSH_STATE_PERIODIC && nNow > nLastWrite + (int64_t)DATABASE_WRITE_INTERVAL * 1000000;
     // It's been very long since we flushed the cache. Do this infrequently, to optimize cache usage.