diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 4b111aa2..db0c4529 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -9,7 +9,7 @@ on:
 # Remember to update me in package-set.yml as well
 env:
   vessel_version: "v0.7.0"
-  moc_version: "0.13.4"
+  moc_version: "0.13.5"
 
 jobs:
   tests:
diff --git a/.github/workflows/package-set.yml b/.github/workflows/package-set.yml
index 5c550722..e704fb42 100644
--- a/.github/workflows/package-set.yml
+++ b/.github/workflows/package-set.yml
@@ -8,7 +8,7 @@ on:
 
 env:
   vessel_version: "v0.7.0"
-  moc_version: "0.13.4"
+  moc_version: "0.13.5"
 
 jobs:
   verify:
diff --git a/CHANGELOG.md b/CHANGELOG.md
index 7afbbec9..af3099d0 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -4,6 +4,8 @@
 
 * Added `Text.fromArray` and `Text.fromVarArray` functions (#674).
 
+* Added `replyDeadline` to `ExperimentalInternetComputer` (#677).
+
 ## 0.13.4
 
 * Breaking change (minor): `Float.format(#hex)` is no longer supported. 
diff --git a/mops.toml b/mops.toml
index 70df5e7d..a2547fd1 100644
--- a/mops.toml
+++ b/mops.toml
@@ -1,6 +1,6 @@
 [package]
 name = "base"
-version = "0.13.4"
+version = "0.13.5"
 description = "The Motoko base library"
 repository = "https://github.com/dfinity/motoko-base"
 keywords = [ "base" ]
@@ -10,5 +10,5 @@ license = "Apache-2.0"
 matchers = "https://github.com/kritzcreek/motoko-matchers#v1.3.0@3dac8a071b69e4e651b25a7d9683fe831eb7cffd"
 
 [toolchain]
-moc = "0.13.4"
+moc = "0.13.5"
 wasmtime = "17.0.0"
diff --git a/src/ExperimentalInternetComputer.mo b/src/ExperimentalInternetComputer.mo
index d7e158be..3a3d4c2d 100644
--- a/src/ExperimentalInternetComputer.mo
+++ b/src/ExperimentalInternetComputer.mo
@@ -82,4 +82,10 @@ module {
   /// ```
   public let performanceCounter : (counter : Nat32) -> (value: Nat64) = Prim.performanceCounter;
 
+  /// Returns the time (in nanoseconds from the epoch start) by when the update message should
+  /// reply to the best effort message so that it can be received by the requesting canister.
+  /// Queries and non-best-effort update messages return zero.
+  ///
+  public func replyDeadline() : Nat = Prim.nat64ToNat(Prim.replyDeadline());
+
 }