diff --git a/src/api/s3/get.rs b/src/api/s3/get.rs
index 888a040a..a1e4ce10 100644
--- a/src/api/s3/get.rs
+++ b/src/api/s3/get.rs
@@ -845,7 +845,9 @@ impl PreconditionHeaders {
 	}
 
 	fn check(&self, v: &ObjectVersion, etag: &str) -> Result<Option<StatusCode>, Error> {
-		let v_date = UNIX_EPOCH + Duration::from_millis(v.timestamp);
+		// we store date with ms precision, but headers are precise to the second: truncate
+		// the timestamp to handle the same-second edge case
+		let v_date = UNIX_EPOCH + Duration::from_secs(v.timestamp / 1000);
 
 		// Implemented from https://datatracker.ietf.org/doc/html/rfc7232#section-6
 
diff --git a/src/garage/tests/s3/objects.rs b/src/garage/tests/s3/objects.rs
index d63ac000..53e8231d 100644
--- a/src/garage/tests/s3/objects.rs
+++ b/src/garage/tests/s3/objects.rs
@@ -198,6 +198,7 @@ async fn test_precondition() {
 		);
 	}
 	let older_date = DateTime::from_secs_f64(last_modified.as_secs_f64() - 10.0);
+	let same_date = DateTime::from_secs_f64(last_modified.as_secs_f64());
 	let newer_date = DateTime::from_secs_f64(last_modified.as_secs_f64() + 10.0);
 	{
 		let err = ctx
@@ -212,6 +213,18 @@ async fn test_precondition() {
 			matches!(err, Err(SdkError::ServiceError(se)) if se.raw().status().as_u16() == 304)
 		);
 
+		let err = ctx
+			.client
+			.get_object()
+			.bucket(&bucket)
+			.key(STD_KEY)
+			.if_modified_since(same_date)
+			.send()
+			.await;
+		assert!(
+			matches!(err, Err(SdkError::ServiceError(se)) if se.raw().status().as_u16() == 304)
+		);
+
 		let o = ctx
 			.client
 			.get_object()
@@ -236,6 +249,17 @@ async fn test_precondition() {
 			matches!(err, Err(SdkError::ServiceError(se)) if se.raw().status().as_u16() == 412)
 		);
 
+		let o = ctx
+			.client
+			.get_object()
+			.bucket(&bucket)
+			.key(STD_KEY)
+			.if_unmodified_since(same_date)
+			.send()
+			.await
+			.unwrap();
+		assert_eq!(o.e_tag.as_ref().unwrap().as_str(), etag);
+
 		let o = ctx
 			.client
 			.get_object()