diff --git a/src.ts/providers/abstract-provider.ts b/src.ts/providers/abstract-provider.ts
index 511db792f3..c53c4b6a2b 100644
--- a/src.ts/providers/abstract-provider.ts
+++ b/src.ts/providers/abstract-provider.ts
@@ -537,10 +537,14 @@ export class AbstractProvider implements Provider {
             return toQuantity(blockTag);
         }
 
+        if (typeof(blockTag) === "bigint") {
+            blockTag = getNumber(blockTag, "blockTag");
+        }
+
         if (typeof(blockTag) === "number") {
             if (blockTag >= 0) { return toQuantity(blockTag); }
             if (this.#lastBlockNumber >= 0) { return toQuantity(this.#lastBlockNumber + blockTag); }
-            return this.getBlockNumber().then((b) => toQuantity(b + blockTag));
+            return this.getBlockNumber().then((b) => toQuantity(b + <number>blockTag));
         }
 
         assertArgument(false, "invalid blockTag", "blockTag", blockTag);
diff --git a/src.ts/providers/provider.ts b/src.ts/providers/provider.ts
index 528a75b477..5731f8fea8 100644
--- a/src.ts/providers/provider.ts
+++ b/src.ts/providers/provider.ts
@@ -16,7 +16,7 @@ import type { Network } from "./network.js";
 
 const BN_0 = BigInt(0);
 
-export type BlockTag = number | string;
+export type BlockTag = BigNumberish | string;
 
 import {
     BlockParams, LogParams, TransactionReceiptParams,