diff --git a/src/util/uint64.spec.ts b/src/util/uint64.spec.ts
index c4ec04fed..7917b6751 100644
--- a/src/util/uint64.spec.ts
+++ b/src/util/uint64.spec.ts
@@ -41,6 +41,7 @@ describe("uint64", () => {
     expect(new Uint64(4294967295, 4294967295).toString(36)).toEqual(
       "3w5e11264sgsf",
     );
+    expect(new Uint64(0, 79741775).toString(29)).toEqual("s2276dsssss2");
   });
 
   it("conversion from string", () => {
@@ -110,7 +111,7 @@ describe("uint64", () => {
       expect(u.toString(13)).toEqual("153c9125c642b111b8");
       check(u, 13);
     }
-
+    check(new Uint64(0, 79741775), 29);
     for (let base = 2; base <= 36; ++base) {
       for (let i = 0; i < count; ++i) {
         check(Uint64.random(), base);
diff --git a/src/util/uint64.ts b/src/util/uint64.ts
index 32830283c..7a05caddc 100644
--- a/src/util/uint64.ts
+++ b/src/util/uint64.ts
@@ -105,7 +105,7 @@ export class Uint64 {
     vHigh *= trueBase;
     const { lowBase, lowDigits } = stringConversionData[base];
     const vHighExtra = vHigh % lowBase;
-    vHigh = Math.floor(vHigh / lowBase);
+    vHigh = Number(BigInt(vHigh) / BigInt(lowBase));
     vLow += vHighExtra;
     vHigh += Math.floor(vLow / lowBase);
     vLow = vLow % lowBase;