diff --git a/src/libraries/Verifier.sol b/src/libraries/Verifier.sol
index b34e247..d48c241 100644
--- a/src/libraries/Verifier.sol
+++ b/src/libraries/Verifier.sol
@@ -21,7 +21,7 @@ library Verifier {
         uint256 s
     ) internal view returns (bool) {
         if (px >= P || rx >= P || s >= N || s == 0) { return false; }
-        if (rx < N) { return verifySpectre(call, px, rx, s); }
+        if (px < N) { return verifySpectre(call, px, rx, s); }
         return verifyBanshee(call, px, rx, s);
     }
 
@@ -38,6 +38,8 @@ library Verifier {
         // Explanation: https://hackmd.io/@nZ-twauPRISEa6G9zg3XRw/SyjJzSLt9
         bytes32 sp = bytes32(N - mulmod(s, px, N));
         bytes32 ep = bytes32(N - mulmod(e, px, N));
+        if (sp == 0) { return false; }
+        if (ep == 0) { return false; }
 
         // Parity should be always even
         address recoveredR = ecrecover(sp, 27, bytes32(px), ep);