diff --git a/soroban-spec/fixtures/ts/package.json b/soroban-spec/fixtures/ts/package.json
index a5f6605ce..15f71b1dc 100644
--- a/soroban-spec/fixtures/ts/package.json
+++ b/soroban-spec/fixtures/ts/package.json
@@ -5,17 +5,18 @@
         "@stellar/freighter-api": "1.4.0",
         "buffer": "6.0.3",
         "soroban-client": "0.8.0",
-        "bigint-conversion": "2.4.1"
+        "bigint-conversion": "2.4.1",
+        "stellar-base": "9.0.0-soroban.3"
     },
     "scripts": {
         "build": "node ./scripts/build.mjs"
     },
     "exports": {
-      "require": "./dist/cjs/index.js",
-      "import": "./dist/esm/index.js"
+        "require": "./dist/cjs/index.js",
+        "import": "./dist/esm/index.js"
     },
     "typings": "dist/types/index.d.ts",
     "devDependencies": {
         "typescript": "5.0.4"
     }
-}
+}
\ No newline at end of file
diff --git a/soroban-spec/fixtures/ts/src/convert.ts b/soroban-spec/fixtures/ts/src/convert.ts
index 647fb5997..da2006fcf 100644
--- a/soroban-spec/fixtures/ts/src/convert.ts
+++ b/soroban-spec/fixtures/ts/src/convert.ts
@@ -130,3 +130,17 @@ export function addressToScVal(addr: string): xdr.ScVal {
     let addrObj = Address.fromString(addr);
     return addrObj.toScVal();
 }
+
+export function i128ToScVal(i: bigint): xdr.ScVal {
+    return xdr.ScVal.scvI128(new xdr.Int128Parts({
+        lo: xdr.Uint64.fromString((i & BigInt(0xFFFFFFFFFFFFFFFFn)).toString()),
+        hi: xdr.Int64.fromString(((i >> BigInt(64)) & BigInt(0xFFFFFFFFFFFFFFFFn)).toString()),
+    }))
+}
+
+export function u128ToScVal(i: bigint): xdr.ScVal {
+    return xdr.ScVal.scvU128(new xdr.UInt128Parts({
+        lo: xdr.Uint64.fromString((i & BigInt(0xFFFFFFFFFFFFFFFFn)).toString()),
+        hi: xdr.Int64.fromString(((i >> BigInt(64)) & BigInt(0xFFFFFFFFFFFFFFFFn)).toString()),
+    }))
+}
\ No newline at end of file
diff --git a/soroban-spec/fixtures/ts/src/index.ts b/soroban-spec/fixtures/ts/src/index.ts
index b7b74679a..fdd3c5765 100644
--- a/soroban-spec/fixtures/ts/src/index.ts
+++ b/soroban-spec/fixtures/ts/src/index.ts
@@ -1,7 +1,7 @@
 import * as SorobanClient from 'soroban-client';
 import { xdr } from 'soroban-client';
 import { Buffer } from "buffer";
-import { scValStrToJs, scValToJs, addressToScVal } from './convert.js';
+import { scValStrToJs, scValToJs, addressToScVal, u128ToScVal, i128ToScVal } from './convert.js';
 import { invoke, InvokeArgs } from './invoke.js';
 
 declare const Errors: { message: string }[]
diff --git a/soroban-spec/src/gen/typescript/project_template/package.json b/soroban-spec/src/gen/typescript/project_template/package.json
index 4902e4f13..29ad833e9 100644
--- a/soroban-spec/src/gen/typescript/project_template/package.json
+++ b/soroban-spec/src/gen/typescript/project_template/package.json
@@ -5,17 +5,18 @@
         "@stellar/freighter-api": "1.4.0",
         "buffer": "6.0.3",
         "soroban-client": "0.8.0",
-        "bigint-conversion": "2.4.1"
+        "bigint-conversion": "2.4.1",
+        "stellar-base": "9.0.0-soroban.3"
     },
     "scripts": {
         "build": "node ./scripts/build.mjs"
     },
     "exports": {
-      "require": "./dist/cjs/index.js",
-      "import": "./dist/esm/index.js"
+        "require": "./dist/cjs/index.js",
+        "import": "./dist/esm/index.js"
     },
     "typings": "dist/types/index.d.ts",
     "devDependencies": {
         "typescript": "5.0.4"
     }
-}
+}
\ No newline at end of file
diff --git a/soroban-spec/src/gen/typescript/project_template/src/convert.ts b/soroban-spec/src/gen/typescript/project_template/src/convert.ts
index 647fb5997..da2006fcf 100644
--- a/soroban-spec/src/gen/typescript/project_template/src/convert.ts
+++ b/soroban-spec/src/gen/typescript/project_template/src/convert.ts
@@ -130,3 +130,17 @@ export function addressToScVal(addr: string): xdr.ScVal {
     let addrObj = Address.fromString(addr);
     return addrObj.toScVal();
 }
+
+export function i128ToScVal(i: bigint): xdr.ScVal {
+    return xdr.ScVal.scvI128(new xdr.Int128Parts({
+        lo: xdr.Uint64.fromString((i & BigInt(0xFFFFFFFFFFFFFFFFn)).toString()),
+        hi: xdr.Int64.fromString(((i >> BigInt(64)) & BigInt(0xFFFFFFFFFFFFFFFFn)).toString()),
+    }))
+}
+
+export function u128ToScVal(i: bigint): xdr.ScVal {
+    return xdr.ScVal.scvU128(new xdr.UInt128Parts({
+        lo: xdr.Uint64.fromString((i & BigInt(0xFFFFFFFFFFFFFFFFn)).toString()),
+        hi: xdr.Int64.fromString(((i >> BigInt(64)) & BigInt(0xFFFFFFFFFFFFFFFFn)).toString()),
+    }))
+}
\ No newline at end of file
diff --git a/soroban-spec/src/gen/typescript/project_template/src/index.ts b/soroban-spec/src/gen/typescript/project_template/src/index.ts
index 0cd3a6f2a..6255cc544 100644
--- a/soroban-spec/src/gen/typescript/project_template/src/index.ts
+++ b/soroban-spec/src/gen/typescript/project_template/src/index.ts
@@ -1,7 +1,7 @@
 import * as SorobanClient from 'soroban-client';
 import { xdr } from 'soroban-client';
 import { Buffer } from "buffer";
-import { scValStrToJs, scValToJs, addressToScVal } from './convert.js';
+import { scValStrToJs, scValToJs, addressToScVal, u128ToScVal, i128ToScVal } from './convert.js';
 import { invoke, InvokeArgs } from './invoke.js';
 
 declare const Errors: { message: string }[]
diff --git a/soroban-spec/src/gen/typescript/wrapper.rs b/soroban-spec/src/gen/typescript/wrapper.rs
index ecb6134e5..6b1425491 100644
--- a/soroban-spec/src/gen/typescript/wrapper.rs
+++ b/soroban-spec/src/gen/typescript/wrapper.rs
@@ -45,12 +45,8 @@ pub fn type_to_js_xdr(value: &types::Type) -> String {
         types::Type::Bytes => "xdr.ScVal.scvBytes(i)".to_owned(),
         types::Type::Address => "addressToScVal(i)".to_owned(),
         types::Type::Void => "xdr.ScVal.scvVoid()".to_owned(),
-        types::Type::U128 => {
-            "xdr.ScVal.scvU128(xdr.Int128Parts.fromXDR(i.toString(16), 'hex'))".to_owned()
-        }
-        types::Type::I128 => {
-            "xdr.ScVal.scvI128(xdr.Int128Parts.fromXDR(i.toString(16), 'hex'))".to_owned()
-        }
+        types::Type::U128 => "u128ToScVal(i)".to_owned(),
+        types::Type::I128 => "i128ToScVal(i)".to_owned(),
         types::Type::I256 => todo!(),
         types::Type::U256 => todo!(),
         types::Type::String => "xdr.ScVal.scvString(i)".to_owned(),