diff --git a/app/app_test.go b/app/app_test.go
index b4399fb..269b295 100644
--- a/app/app_test.go
+++ b/app/app_test.go
@@ -35,7 +35,7 @@ func TestBadSpendMsg(t *testing.T) {
 
 	// Construct a SpendMsg
 	var msg = types.SpendMsg{
-		Blknum1:      0,
+		Blknum1:      1,
 		Txindex1:     0,
 		Oindex1:      0,
 		DepositNum1:  0,
diff --git a/types/tx.go b/types/tx.go
index 74dc88e..d667763 100644
--- a/types/tx.go
+++ b/types/tx.go
@@ -65,6 +65,9 @@ func (msg SpendMsg) ValidateBasic() sdk.Error {
 	if !utils.ValidAddress(msg.Newowner1) {
 		return ErrInvalidAddress(DefaultCodespace, "No recipients of transaction")
 	}
+	if msg.Blknum1 == msg.Blknum2 && msg.Txindex1 == msg.Txindex2 && msg.Oindex1 == msg.Oindex2 && msg.DepositNum1 == msg.DepositNum2 {
+		return ErrInvalidTransaction(DefaultCodespace, "Cannot spend same position twice")
+	}
 
 	switch {
 
diff --git a/types/tx_test.go b/types/tx_test.go
index aa55cd4..c513f31 100644
--- a/types/tx_test.go
+++ b/types/tx_test.go
@@ -116,6 +116,16 @@ func TestInvalidSpendDeposit(t *testing.T) {
 	assert.Equal(t, sdk.CodeType(106), err.Code(), err.Error())
 }
 
+// Creates an invalid transaction spending same position twice
+func TestInvalidPosition(t *testing.T) {
+	var msg1 = GenSpendMsgWithAddresses()
+	// Set second position equal to first position
+	msg1.Txindex2 = 0
+
+	err := msg1.ValidateBasic()
+	assert.Equal(t, sdk.CodeType(106), err.Code(), err.Error())
+}
+
 // Tests GetSigners method
 func TestGetSigners(t *testing.T) {
 	msg := GenBasicSpendMsg()