error: UniswapV2: K

[busytoby]

Bug Description
I have attempted to sell any of these three tokens:
FIRE: 0x3F8A2f7bcD70e7F7Bdd3FbB079c11d073588DEA2
AST: 0xa872E0a44BBd66c1486a756CB5BD3F0bEEC4e32e
PAMP: 0xF0FAC7104aAC544e4a7CE1A55ADF2B5a25c65bD1

For any sale of these tokens the UI is reporting:
The transaction cannot succeed due to error: UniswapV2: K. This is probably an issue with one of the tokens you are swapping.

This is prior to any confirmation popup from metamask, no confirmation ever pops.

If I continue to try over an hour or more I can eventually get a transaction to initiate but then the error returns some short time later.

Steps to Reproduce

1. Attempt to sell any of the 3 tokens above, or presumedly any token which is deflationary on transfer
2. Notice the error popup on the website, the transaction never makes it to metamask
   ...

[busytoby]

This appears to be a Uniswap UI bug.
If I try to sell any deflationary token for a specific amount of ETH ie: Sell from wallet balance for 0.25 ETH, the UI computes an invalid digit length and the transaction fails.

If I instead try to sell an exact number from the deflationary token balance ie: 1000 AST for whatever amount of ETH, the transaction is posted to MetaMask and succeeds as expected.

[ragle]

Right. I was likewise able to get around this by just using a round number for the deflationary token I wanted to swap for ETH.

[moodysalem]

It depends on the token. If the token has rebases similar to how AMPL works, it may cause the pair to break and throw this error, until someone calls sync on the pair contract. If it collects a fee on transfer, you can increase your slippage tolerance to account for the fee.

[CryptoGnome]

I have seen this error as well more than once, here is a example TX:
https://etherscan.io/tx/0x4754dd19fe79179d5e0e511fa90311f6b1141eed62d4eee55d617d6932245ee3

[pplonski]

I've got this error without using UI.

I want to manually swap exact token (6d6506e6f438ede269877a0a720026559110b7d5) to token (f0fac7104aac544e4a7ce1a55adf2b5a25c65bd1) by calling a router (0x7a250d5630b4cf539739df2c5dacb4c659f2488d)

The function that I call:

swapExactTokensForTokens(uint256 amountIn, uint256 amountOutMin, address[] path, address to, uint256 deadline)

input data used:

# | Name | Type | Data
-- | -- | -- | --
0 | amountIn | uint256 | 737594127022435509
1 | amountOutMin | uint256 | 1
2 | path | address[] | 6d6506e6f438ede269877a0a720026559110b7d5f0fac7104aac544e4a7ce1a55adf2b5a25c65bd1
3 | to | address | 89797ff78cd4f1a0a6ded5ea7b389ed414e108db
4 | deadline | uint256 | 4901989959

Transaction: https://etherscan.io/tx/0x2d366f44aba71e0d76e54e1701c4bde2cbd8e17c4422ef99f17cbc921860d801

It would be nice to know which tokens can be used in the swap and which can not. How to check that?

[VanijaDev]

Same issue here. Using Uniswap API

[dmamira]

Same issue.

[CryptoGnome]

Attempt to raise gas limit on pairs with burn or other weird functions..

[fernandezpaco]

Any update on this? I'm getting same error.

If i call getAmountOut i get:
[ '2000000000000000000', '8929646551579217460990', '260279713853141966224', '2012937985424733095' ]

But if i try the swap (swapExactETHForTokens) i get:
{ Error: Returned error: execution reverted: UniswapV2: K }

My example path:
0xc02aaa39b223fe8d0a0e5c4f27ead9083c756cc2,0xD04785C4d8195e4A54d9dEc3a9043872875ae9E2,0x1f9840a85d5af5bf1d1762f925bdaddc4201f984,0xC02aaA39b223FE8D0A0e5C4F27eAD9083C756Cc2

Thanks

[jitendermalik]

got same issue , any help on this is appreciated

[tokyo786]

@jitendermalik @fernandezpaco @pplonski
Have you guys tried the swapExactTokensForETHSupportingFeeOnTransferTokens [or similar functions instead?] - since the token is collecting a fee on transfer, you may want to try those functions. Probably enabling supporting fee on transfer tokens might help.

https://uniswap.org/docs/v2/smart-contracts/router02

[sabotagebeats]

found this error with rebasing token, calling poolContract.sync() fixed it.

[jitendermalik]

found this error with rebasing token, calling poolContract.sync() fixed it.

Is this fixed deployed in production ?

[jitendermalik]

https://uniswap.org/docs/v2/smart-contracts/router02
@tokyo786 I am writing proxy contract which will be used for multiple tokens. I do not think all pairs support this
swapExactTokensForETHSupportingFeeOnTransferTokens , How to identify which token support fee on transfer