diff --git a/src/miner.h b/src/miner.h
index 4c8d6ef5b..7123d3072 100644
--- a/src/miner.h
+++ b/src/miner.h
@@ -73,7 +73,7 @@ struct modifiedentry_iter {
 // except operating on CTxMemPoolModifiedEntry.
 // TODO: refactor to avoid duplication of this logic.
 struct CompareModifiedEntry {
-    bool operator()(const CTxMemPoolModifiedEntry &a, const CTxMemPoolModifiedEntry &b)
+    bool operator()(const CTxMemPoolModifiedEntry &a, const CTxMemPoolModifiedEntry &b) const
     {
         double f1 = (double)a.nModFeesWithAncestors * b.nSizeWithAncestors;
         double f2 = (double)b.nModFeesWithAncestors * a.nSizeWithAncestors;
@@ -88,7 +88,7 @@ struct CompareModifiedEntry {
 // This is sufficient to sort an ancestor package in an order that is valid
 // to appear in a block.
 struct CompareTxIterByAncestorCount {
-    bool operator()(const CTxMemPool::txiter &a, const CTxMemPool::txiter &b)
+    bool operator()(const CTxMemPool::txiter &a, const CTxMemPool::txiter &b) const
     {
         if (a->GetCountWithAncestors() != b->GetCountWithAncestors())
             return a->GetCountWithAncestors() < b->GetCountWithAncestors();
diff --git a/src/txmempool.h b/src/txmempool.h
index 82c50a65c..6a16c6d50 100644
--- a/src/txmempool.h
+++ b/src/txmempool.h
@@ -224,7 +224,7 @@ struct mempoolentry_txid
 class CompareTxMemPoolEntryByDescendantScore
 {
 public:
-    bool operator()(const CTxMemPoolEntry& a, const CTxMemPoolEntry& b)
+    bool operator()(const CTxMemPoolEntry& a, const CTxMemPoolEntry& b) const
     {
         bool fUseADescendants = UseDescendantScore(a);
         bool fUseBDescendants = UseDescendantScore(b);
@@ -246,7 +246,7 @@ public:
     }
 
     // Calculate which score to use for an entry (avoiding division).
-    bool UseDescendantScore(const CTxMemPoolEntry &a)
+    bool UseDescendantScore(const CTxMemPoolEntry &a) const
     {
         double f1 = (double)a.GetModifiedFee() * a.GetSizeWithDescendants();
         double f2 = (double)a.GetModFeesWithDescendants() * a.GetTxSize();
@@ -261,7 +261,7 @@ public:
 class CompareTxMemPoolEntryByScore
 {
 public:
-    bool operator()(const CTxMemPoolEntry& a, const CTxMemPoolEntry& b)
+    bool operator()(const CTxMemPoolEntry& a, const CTxMemPoolEntry& b) const
     {
         double f1 = (double)a.GetModifiedFee() * b.GetTxSize();
         double f2 = (double)b.GetModifiedFee() * a.GetTxSize();
@@ -275,7 +275,7 @@ public:
 class CompareTxMemPoolEntryByEntryTime
 {
 public:
-    bool operator()(const CTxMemPoolEntry& a, const CTxMemPoolEntry& b)
+    bool operator()(const CTxMemPoolEntry& a, const CTxMemPoolEntry& b) const
     {
         return a.GetTime() < b.GetTime();
     }
@@ -284,7 +284,7 @@ public:
 class CompareTxMemPoolEntryByAncestorFee
 {
 public:
-    bool operator()(const CTxMemPoolEntry& a, const CTxMemPoolEntry& b)
+    bool operator()(const CTxMemPoolEntry& a, const CTxMemPoolEntry& b) const
     {
         double aFees = a.GetModFeesWithAncestors();
         double aSize = a.GetSizeWithAncestors();