diff --git a/pkg/core/blockchain.go b/pkg/core/blockchain.go
index 59e4bc5b5..0365c2517 100644
--- a/pkg/core/blockchain.go
+++ b/pkg/core/blockchain.go
@@ -1045,14 +1045,17 @@ func (bc *Blockchain) VerifyWitnesses(t *transaction.Transaction) error {
 		if vm.HasFailed() {
 			return errors.Errorf("vm failed to execute the script")
 		}
-		res := vm.PopResult()
-		switch res.(type) {
-		case bool:
-			if !(res.(bool)) {
+		resEl := vm.Estack().Pop()
+		if resEl != nil {
+			res, err := resEl.TryBool()
+			if err != nil {
+				return err
+			}
+			if !res {
 				return errors.Errorf("signature check failed")
 			}
-		default:
-			return errors.Errorf("vm returned non-boolean result")
+		} else {
+			return errors.Errorf("no result returned from the script")
 		}
 	}
 
diff --git a/pkg/vm/stack.go b/pkg/vm/stack.go
index c9ce195be..5dd5b2dd1 100644
--- a/pkg/vm/stack.go
+++ b/pkg/vm/stack.go
@@ -80,30 +80,40 @@ func (e *Element) BigInt() *big.Int {
 	}
 }
 
-// Bool attempts to get the underlying value of the element as a boolean.
-// Will panic if the assertion failed which will be caught by the VM.
-func (e *Element) Bool() bool {
+// TryBool attempts to get the underlying value of the element as a boolean.
+// Returns error if can't convert value to boolean type.
+func (e *Element) TryBool() (bool, error) {
 	switch t := e.value.(type) {
 	case *BigIntegerItem:
-		return t.value.Int64() != 0
+		return t.value.Int64() != 0, nil
 	case *BoolItem:
-		return t.value
+		return t.value, nil
 	case *ArrayItem, *StructItem:
-		return true
+		return true, nil
 	case *ByteArrayItem:
 		for _, b := range t.value {
 			if b != 0 {
-				return true
+				return true, nil
 			}
 		}
-		return false
+		return false, nil
 	case *InteropItem:
-		return t.value != nil
+		return t.value != nil, nil
 	default:
-		panic("can't convert to bool: " + t.String())
+		return false, fmt.Errorf("can't convert to bool: " + t.String())
 	}
 }
 
+// Bool attempts to get the underlying value of the element as a boolean.
+// Will panic if the assertion failed which will be caught by the VM.
+func (e *Element) Bool() bool {
+	val, err := e.TryBool()
+	if err != nil {
+		panic(err)
+	}
+	return val
+}
+
 // Bytes attempts to get the underlying value of the element as a byte array.
 // Will panic if the assertion failed which will be caught by the VM.
 func (e *Element) Bytes() []byte {