diff --git a/src/mining/score_bpp9000.h b/src/mining/score_bpp9000.h
index 6152ab28..b7f308b4 100644
--- a/src/mining/score_bpp9000.h
+++ b/src/mining/score_bpp9000.h
@@ -8,6 +8,19 @@
 namespace score_engine
 {
 
+// Largest L (mutations per step) the scorer clamps nonce[1] to
+static constexpr unsigned int MAX_LUT_ENTRIES_PER_STEP = 10;
+
+// A bpp9000 nonce is canonical iff its score-irrelevant knob bytes are canonical:
+// nonce[0] = algo (enforced by routing), nonce[1] = L in [1, MAX_LUT_ENTRIES_PER_STEP], nonce[2] = K = 0
+static bool isCanonicalBpp9000Nonce(const unsigned char* nonce)
+{
+    return (getAlgoType(nonce) == AlgoType::Bpp9000)
+        && (nonce[1] >= 1)
+        && (nonce[1] <= MAX_LUT_ENTRIES_PER_STEP)
+        && (nonce[2] == 0);
+}
+
 template<typename Params>
 struct ScoreBpp9000
 {
@@ -29,7 +42,6 @@ struct ScoreBpp9000
     static constexpr unsigned long long lutSize = 27;
     // LUT row storage stride, padded to 32; only leading lutSize entries logical (index <= 26).
     static constexpr unsigned long long lutStride = 32;
-    static constexpr unsigned int MAX_LUT_ENTRIES_PER_STEP = 10;
 
     static_assert(lutSize <= lutStride, "LUT rows must fit the padded stride");
 
diff --git a/src/public_settings.h b/src/public_settings.h
index 7e21e380..92060605 100644
--- a/src/public_settings.h
+++ b/src/public_settings.h
@@ -71,7 +71,7 @@ static_assert(AUTO_FORCE_NEXT_TICK_THRESHOLD* TARGET_TICK_DURATION >= PEER_REFRE
 
 #define VERSION_A 1
 #define VERSION_B 301
-#define VERSION_C 0
+#define VERSION_C 2
 
 // Epoch and initial tick for node startup
 #define EPOCH 224
@@ -126,6 +126,10 @@ static constexpr unsigned long long BPP9000_NUMBER_OF_MUTATIONS = 100;
 static constexpr unsigned long long BPP9000_NUMBER_OF_WINDOWS = BPP9000_SEQUENCE_LENGTH - BPP9000_WINDOW_WIDTH;
 static constexpr unsigned int BPP9000_SOLUTION_THRESHOLD_DEFAULT = 3838;
 
+// From this tick, bpp9000 solutions whose nonce is non-canonical (nonce[1] outside [1, MAX_LUT_ENTRIES_PER_STEP]
+// or nonce[2] != 0) are rejected as invalid
+static constexpr unsigned int BPP9000_NONCE_CANONICAL_ACTIVATION_TICK = 70900000;
+
 
 // Multipler of score
 static constexpr unsigned int NEURAXON_SOLUTION_MULTIPLER = 1;
diff --git a/src/qubic.cpp b/src/qubic.cpp
index 7b5368ba..03dd1a28 100644
--- a/src/qubic.cpp
+++ b/src/qubic.cpp
@@ -636,7 +636,8 @@ static void processBroadcastMessage(const unsigned long long processorNumber, Re
                                         }
                                         if (k == system.numberOfSolutions)
                                         {
-                                            unsigned int solutionScore = (*score)(processorNumber, request->destinationPublicKey, solution_miningSeed, solution_nonce);
+                                            unsigned int solutionScore = (system.tick >= BPP9000_NONCE_CANONICAL_ACTIVATION_TICK && !score_engine::isCanonicalBpp9000Nonce(solution_nonce.m256i_u8)) ? 
+                                                score_engine::INVALID_SCORE_VALUE : (*score)(processorNumber, request->destinationPublicKey, solution_miningSeed, solution_nonce);
                                             score_engine::AlgoType selectedAlgo = score_engine::getAlgoType(solution_nonce.m256i_u8);
                                             const int threshold = getSolutionThreshold(selectedAlgo);
                                             if (system.numberOfSolutions < MAX_NUMBER_OF_SOLUTIONS
@@ -1015,7 +1016,10 @@ static void processBroadcastTransaction(Peer* peer, RequestResponseHeader* heade
                 {
                     const m256i& solutionMiningSeed = *(m256i*)request->inputPtr();
                     const m256i& solutionNonce = *(m256i*)(request->inputPtr() + 32);
-                    (*score)(processorNumber, request->sourcePublicKey, solutionMiningSeed, solutionNonce);
+                    if (system.tick < BPP9000_NONCE_CANONICAL_ACTIVATION_TICK || score_engine::isCanonicalBpp9000Nonce(solutionNonce.m256i_u8))
+                    { 
+                        (*score)(processorNumber, request->sourcePublicKey, solutionMiningSeed, solutionNonce); 
+                    }
                 }
             }
 
@@ -2500,7 +2504,8 @@ static void processTickTransactionSolution(const MiningSolutionTransaction* tran
         minerSolutionFlags[flagIndices[0] >> 6] |= (1ULL << (flagIndices[0] & 63));
         minerSolutionFlags[flagIndices[1] >> 6] |= (1ULL << (flagIndices[1] & 63));
 
-        unsigned int solutionScore = (*::score)(processorNumber, transaction->sourcePublicKey, transaction->miningSeed, transaction->nonce);
+        unsigned int solutionScore = (system.tick >= BPP9000_NONCE_CANONICAL_ACTIVATION_TICK && !score_engine::isCanonicalBpp9000Nonce(transaction->nonce.m256i_u8)) ?
+            score_engine::INVALID_SCORE_VALUE : (*::score)(processorNumber, transaction->sourcePublicKey, transaction->miningSeed, transaction->nonce);
         score_engine::AlgoType selectedAlgo = score_engine::getAlgoType(transaction->nonce.m256i_u8);
         if (score->isValidScore(solutionScore, selectedAlgo))
         {