diff --git a/src/soroban.ts b/src/soroban.ts
index 9792d54..4f3bd06 100644
--- a/src/soroban.ts
+++ b/src/soroban.ts
@@ -512,6 +512,14 @@ export async function queryXlmBalance(
  */
 export const DEFAULT_RESOURCE_FEE_ESTIMATE = 1_000_000n;
 
+/**
+ * Larger fallback used for expensive operations that deploy or instantiate
+ * contracts (e.g. `create_stream`). This is a conservative default sized in
+ * stroops (3 XLM) to avoid under-estimating required balance in the
+ * insufficient-balance error path when the simulation carries no fee fields.
+ */
+export const CREATE_RESOURCE_FEE_ESTIMATE = 30_000_000n;
+
 /**
  * Estimate the minimum resource fee required for a transaction simulation.
  *
diff --git a/src/streams.ts b/src/streams.ts
index 26c725c..55db40d 100644
--- a/src/streams.ts
+++ b/src/streams.ts
@@ -31,6 +31,7 @@ import {
   catchNetworkError,
   queryXlmBalance,
   estimateRequiredFee,
+  CREATE_RESOURCE_FEE_ESTIMATE,
   DEFAULT_RPC,
   NETWORK_PASSPHRASE,
   DEFAULT_CONFIRMATION_MAX_ATTEMPTS,
@@ -258,7 +259,7 @@ export class StreamsModule {
       // query the actual XLM balance and estimate the required fee.
       if (err instanceof InsufficientBalanceError && err.currentBalance === 0n && err.requiredBalance === 0n) {
         const xlmBalance = await queryXlmBalance(this.rpcUrl, this.passphrase, senderAddr).catch(() => 0n);
-        const requiredFee = estimateRequiredFee(sim);
+        const requiredFee = estimateRequiredFee(sim, CREATE_RESOURCE_FEE_ESTIMATE);
         const required = depositStroops + requiredFee;
         throw new InsufficientBalanceError(xlmBalance, required, sim.error);
       }