diff --git a/temporal_capi/bindings/c/I128Nanoseconds.h b/temporal_capi/bindings/c/I128Nanoseconds.h
index 4ac54898f..b026864d6 100644
--- a/temporal_capi/bindings/c/I128Nanoseconds.h
+++ b/temporal_capi/bindings/c/I128Nanoseconds.h
@@ -15,6 +15,8 @@
 
 
 
+bool temporal_rs_I128Nanoseconds_is_valid(I128Nanoseconds self);
+
 
 
 
diff --git a/temporal_capi/bindings/cpp/temporal_rs/I128Nanoseconds.d.hpp b/temporal_capi/bindings/cpp/temporal_rs/I128Nanoseconds.d.hpp
index 68d117aa8..ec1bac566 100644
--- a/temporal_capi/bindings/cpp/temporal_rs/I128Nanoseconds.d.hpp
+++ b/temporal_capi/bindings/cpp/temporal_rs/I128Nanoseconds.d.hpp
@@ -36,6 +36,8 @@ struct I128Nanoseconds {
   int64_t high;
   uint64_t low;
 
+  inline bool is_valid() const;
+
   inline temporal_rs::capi::I128Nanoseconds AsFFI() const;
   inline static temporal_rs::I128Nanoseconds FromFFI(temporal_rs::capi::I128Nanoseconds c_struct);
 };
diff --git a/temporal_capi/bindings/cpp/temporal_rs/I128Nanoseconds.hpp b/temporal_capi/bindings/cpp/temporal_rs/I128Nanoseconds.hpp
index 37115c2bb..1e736be51 100644
--- a/temporal_capi/bindings/cpp/temporal_rs/I128Nanoseconds.hpp
+++ b/temporal_capi/bindings/cpp/temporal_rs/I128Nanoseconds.hpp
@@ -18,10 +18,17 @@ namespace temporal_rs {
 namespace capi {
     extern "C" {
 
+    bool temporal_rs_I128Nanoseconds_is_valid(temporal_rs::capi::I128Nanoseconds self);
+
     } // extern "C"
 } // namespace capi
 } // namespace
 
+inline bool temporal_rs::I128Nanoseconds::is_valid() const {
+  auto result = temporal_rs::capi::temporal_rs_I128Nanoseconds_is_valid(this->AsFFI());
+  return result;
+}
+
 
 inline temporal_rs::capi::I128Nanoseconds temporal_rs::I128Nanoseconds::AsFFI() const {
   return temporal_rs::capi::I128Nanoseconds {
diff --git a/temporal_capi/src/instant.rs b/temporal_capi/src/instant.rs
index 01fbfe6cf..8acf2c6c6 100644
--- a/temporal_capi/src/instant.rs
+++ b/temporal_capi/src/instant.rs
@@ -30,6 +30,13 @@ pub mod ffi {
         pub low: u64,
     }
 
+    impl I128Nanoseconds {
+        pub fn is_valid(self) -> bool {
+            let ns = i128::from(self);
+            temporal_rs::unix_time::EpochNanoseconds::try_from(ns).is_ok()
+        }
+    }
+
     impl Instant {
         pub fn try_new(ns: I128Nanoseconds) -> Result<Box<Self>, TemporalError> {
             temporal_rs::Instant::try_new(ns.into())