diff --git a/src/pow.cpp b/src/pow.cpp
index 1daf60e61..1996307dd 100644
--- a/src/pow.cpp
+++ b/src/pow.cpp
@@ -804,8 +804,20 @@ bool CheckRandomXSolution(const CBlockHeader *pblock, int32_t height)
 
     // Derive the key (shared helper) and serialize the input (identical bytes to the pool path).
     std::string rxKey = GetRandomXKey(height);
-    if (rxKey.empty())
-        return error("CheckRandomXSolution(): cannot derive RandomX key for height %d", height);
+    if (rxKey.empty()) {
+        // The RandomX key block (keyHeight = ((height-lag)/interval)*interval, looked up on the
+        // ACTIVE chain) is not yet connected. This happens ONLY at header-accept when headers run
+        // ahead of our connected block tip (the IBD tail / catch-up) -- block-connect always has it,
+        // since blocks connect in order and keyHeight <= height-lag < the connected tip. The header
+        // is NOT invalid; we simply cannot verify it YET. Defer to block-connect (which re-checks
+        // with the key present) rather than returning an error -- returning an error here makes
+        // CheckBlockHeader DoS(100)-ban the honest peer that sent a perfectly valid tip header we
+        // just can't check yet (observed live: a post-reindex node banned the whole fleet and stalled
+        // ~2000 blocks short of the tip). Flood protection is preserved for synced nodes (key present
+        // -> real RandomX check) and bounded during catch-up by the per-peer IBD header cap + nMinimumChainWork.
+        LogPrint("net", "CheckRandomXSolution: RandomX key block for height %d not yet connected; deferring verification to block-connect\n", height);
+        return true;
+    }
     std::vector<unsigned char> ssInput = GetRandomXInput(*pblock);
 
     char computedHash[RANDOMX_HASH_SIZE];