diff --git a/contracts/utility_contracts/src/lib.rs b/contracts/utility_contracts/src/lib.rs
index d8ebf43..97830ef 100644
--- a/contracts/utility_contracts/src/lib.rs
+++ b/contracts/utility_contracts/src/lib.rs
@@ -8584,6 +8584,8 @@ impl UtilityContract {
     /// Called internally by the provider when billing a post-paid stream.
     /// Emits `CreditLimitApproached` at 80 % and slashes at 100 %.
     pub fn accrue_postpaid_debt(env: Env, owner: Address, debt_amount: i128) {
+    pub fn accrue_postpaid_debt(env: Env, owner: Address, debt_amount: i128) {
+        owner.require_auth();
         if debt_amount <= 0 {
             return;
         }
@@ -8770,4 +8772,4 @@ fn negate_g1(env: &Env, point: &Bytes) -> Bytes {
 }
 
 #[cfg(test)]
-mod zk_tests;
+mod zk_tests;
\ No newline at end of file