diff --git a/actix-files/CHANGES.md b/actix-files/CHANGES.md
index ff8ccd64..9f606dfc 100644
--- a/actix-files/CHANGES.md
+++ b/actix-files/CHANGES.md
@@ -1,7 +1,9 @@
 # Changes
 
 ## Unreleased - 2021-xx-xx
+* Fix If-Modified-Since and If-Unmodified-Since to not compare using sub-second timestamps. [#1887]
 
+[#1887]: https://github.com/actix/actix-web/pull/1887
 
 ## 0.6.0-beta.1 - 2021-01-07
 * `HttpRange::parse` now has its own error type.
diff --git a/actix-files/src/lib.rs b/actix-files/src/lib.rs
index b7225fbc..f4314f6b 100644
--- a/actix-files/src/lib.rs
+++ b/actix-files/src/lib.rs
@@ -107,6 +107,18 @@ mod tests {
         assert_eq!(resp.status(), StatusCode::NOT_MODIFIED);
     }
 
+    #[actix_rt::test]
+    async fn test_if_modified_since_without_if_none_match_same() {
+        let file = NamedFile::open("Cargo.toml").unwrap();
+        let since = file.last_modified().unwrap();
+
+        let req = TestRequest::default()
+            .header(header::IF_MODIFIED_SINCE, since)
+            .to_http_request();
+        let resp = file.respond_to(&req).await.unwrap();
+        assert_eq!(resp.status(), StatusCode::NOT_MODIFIED);
+    }
+
     #[actix_rt::test]
     async fn test_if_modified_since_with_if_none_match() {
         let file = NamedFile::open("Cargo.toml").unwrap();
@@ -121,6 +133,30 @@ mod tests {
         assert_ne!(resp.status(), StatusCode::NOT_MODIFIED);
     }
 
+    #[actix_rt::test]
+    async fn test_if_unmodified_since() {
+        let file = NamedFile::open("Cargo.toml").unwrap();
+        let since = file.last_modified().unwrap();
+
+        let req = TestRequest::default()
+            .header(header::IF_UNMODIFIED_SINCE, since)
+            .to_http_request();
+        let resp = file.respond_to(&req).await.unwrap();
+        assert_eq!(resp.status(), StatusCode::OK);
+    }
+
+    #[actix_rt::test]
+    async fn test_if_unmodified_since_failed() {
+        let file = NamedFile::open("Cargo.toml").unwrap();
+        let since = header::HttpDate::from(SystemTime::UNIX_EPOCH);
+
+        let req = TestRequest::default()
+            .header(header::IF_UNMODIFIED_SINCE, since)
+            .to_http_request();
+        let resp = file.respond_to(&req).await.unwrap();
+        assert_eq!(resp.status(), StatusCode::PRECONDITION_FAILED);
+    }
+
     #[actix_rt::test]
     async fn test_named_file_text() {
         assert!(NamedFile::open("test--").is_err());
diff --git a/actix-files/src/named.rs b/actix-files/src/named.rs
index b3c247b1..dc461e29 100644
--- a/actix-files/src/named.rs
+++ b/actix-files/src/named.rs
@@ -331,7 +331,7 @@ impl NamedFile {
             let t2: SystemTime = since.clone().into();
 
             match (t1.duration_since(UNIX_EPOCH), t2.duration_since(UNIX_EPOCH)) {
-                (Ok(t1), Ok(t2)) => t1 > t2,
+                (Ok(t1), Ok(t2)) => t1.as_secs() > t2.as_secs(),
                 _ => false,
             }
         } else {
@@ -350,7 +350,7 @@ impl NamedFile {
             let t2: SystemTime = since.clone().into();
 
             match (t1.duration_since(UNIX_EPOCH), t2.duration_since(UNIX_EPOCH)) {
-                (Ok(t1), Ok(t2)) => t1 <= t2,
+                (Ok(t1), Ok(t2)) => t1.as_secs() <= t2.as_secs(),
                 _ => false,
             }
         } else {