diff --git a/ethers/provider.nim b/ethers/provider.nim
index 6050943..2a8badf 100644
--- a/ethers/provider.nim
+++ b/ethers/provider.nim
@@ -27,7 +27,7 @@ type
 method getBlockNumber*(provider: Provider): Future[UInt256] {.base.} =
   doAssert false, "not implemented"
 
-method getBlock*(provider: Provider, tag: BlockTag): Future[Block] {.base.} =
+method getBlock*(provider: Provider, tag: BlockTag): Future[?Block] {.base.} =
   doAssert false, "not implemented"
 
 method call*(provider: Provider, tx: Transaction): Future[seq[byte]] {.base.} =