diff --git a/src/com/bitsofproof/supernode/core/Script.java b/src/com/bitsofproof/supernode/core/Script.java
index fbc901f8..5e662dce 100644
--- a/src/com/bitsofproof/supernode/core/Script.java
+++ b/src/com/bitsofproof/supernode/core/Script.java
@@ -1568,7 +1568,19 @@ else if ( (hashType & 0x1f) == SIGHASH_SINGLE )
 		String cacheKey = c.toString ();
 		synchronized ( validSignatureCache )
 		{
-			return validSignatureCache.contains (cacheKey) || ECKeyPair.verify (hash, sig, pubkey) && validSignatureCache.add (cacheKey);
+			if ( validSignatureCache.contains (cacheKey) )
+			{
+				return true;
+			}
+		}
+		if ( ECKeyPair.verify (hash, sig, pubkey) )
+		{
+			synchronized ( validSignatureCache )
+			{
+				validSignatureCache.add (cacheKey);
+			}
+			return true;
 		}
+		return false;
 	}
 }