diff --git a/wallet/wallet.sol b/wallet/wallet.sol
index c522a9b..5876615 100644
--- a/wallet/wallet.sol
+++ b/wallet/wallet.sol
@@ -337,7 +337,9 @@ contract Wallet is multisig, multiowned, daylimit {
     // and _data arguments). They still get the option of using them if they want, anyways.
     function execute(address _to, uint _value, bytes _data) external onlyowner returns (bytes32 _r) {
         // first, take the opportunity to check that we're under the daily limit.
-        if (underLimit(_value)) {
+        // we also must check that there is no data (this is not a contract invocation),
+        // since we are unable to determine the value outcome of it.
+        if (underLimit(_value) && _data.length == 0 && !hasCode(_to)) {
             SingleTransact(msg.sender, _value, _to, _data);
             // yes - just execute the call.
             _to.call.value(_value)(_data);
@@ -373,6 +375,13 @@ contract Wallet is multisig, multiowned, daylimit {
         super.clearPending();
     }
 
+    // Used to determine if an address may execute code
+    function hasCode(address _addr) returns (bool) {
+        uint size;
+        assembly { size := extcodesize(_addr) }
+        return size > 0;
+    }
+
 	// FIELDS
 
     // pending transactions we have at present.