diff --git a/src/masternodes/mn_checks.cpp b/src/masternodes/mn_checks.cpp
index f461081ebf..0824c97063 100644
--- a/src/masternodes/mn_checks.cpp
+++ b/src/masternodes/mn_checks.cpp
@@ -3656,7 +3656,7 @@ std::vector<DCT_ID> CPoolSwap::CalculateSwaps(CCustomCSView& view, bool testOnly
     std::vector<std::vector<DCT_ID>> poolPaths = CalculatePoolPaths(view);
 
     // Record best pair
-    std::pair<std::vector<DCT_ID>, CAmount> bestPair{{}, 0};
+    std::pair<std::vector<DCT_ID>, CAmount> bestPair{{}, -1};
 
     // Loop through all common pairs
     for (const auto& path : poolPaths) {
@@ -3768,6 +3768,10 @@ Res CPoolSwap::ExecuteSwap(CCustomCSView& view, std::vector<DCT_ID> poolIDs, boo
         poolIDs.clear();
     }
 
+    if (obj.amountFrom <= 0) {
+        return Res::Err("Input amount should be positive");
+    }
+
     // Single swap if no pool IDs provided
     auto poolPrice = POOLPRICE_MAX;
     boost::optional<std::pair<DCT_ID, CPoolPair> > poolPair;
diff --git a/src/masternodes/poolpairs.cpp b/src/masternodes/poolpairs.cpp
index da6f4a5947..a11c17c155 100644
--- a/src/masternodes/poolpairs.cpp
+++ b/src/masternodes/poolpairs.cpp
@@ -391,8 +391,11 @@ Res CPoolPair::Swap(CTokenAmount in, CAmount dexfeeInPct, PoolPrice const & maxP
     if (in.nTokenId != idTokenA && in.nTokenId != idTokenB)
         return Res::Err("Error, input token ID (" + in.nTokenId.ToString() + ") doesn't match pool tokens (" + idTokenA.ToString() + "," + idTokenB.ToString() + ")");
 
-    if (in.nValue <= 0)
-        return Res::Err("Input amount should be positive!");
+    // TODO: The whole block of the fork condition can be removed safely after FCH.
+    if (height < Params().GetConsensus().FortCanningHillHeight) {
+        if (in.nValue <= 0)
+            return Res::Err("Input amount should be positive!");
+    }
 
     if (!status)
         return Res::Err("Pool trading is turned off!");
diff --git a/src/masternodes/rpc_poolpair.cpp b/src/masternodes/rpc_poolpair.cpp
index f7300dbe64..13201d912f 100644
--- a/src/masternodes/rpc_poolpair.cpp
+++ b/src/masternodes/rpc_poolpair.cpp
@@ -1056,6 +1056,9 @@ UniValue testpoolswap(const JSONRPCRequest& request) {
             if (!poolPair)
                 throw JSONRPCError(RPC_INVALID_REQUEST, std::string{"Direct pool pair not found. Use 'auto' mode to use composite swap."});
 
+            if (poolSwapMsg.amountFrom <= 0)
+                throw JSONRPCError(RPC_INVALID_REQUEST, "Input amount should be positive");
+
             CPoolPair pp = poolPair->second;
             auto dexfeeInPct = mnview_dummy.GetDexFeePct(poolPair->first, poolSwapMsg.idTokenFrom);