diff --git a/src/database/mod.rs b/src/database/mod.rs
index 2abd3ee..6c01007 100644
--- a/src/database/mod.rs
+++ b/src/database/mod.rs
@@ -18,6 +18,7 @@ use crate::database::lang::Query;
 use crate::util::hash::{Hash, Hashable};
 use crate::util::LoggerSink;
 use anyhow::{anyhow, Result};
+use chrono::NaiveDateTime;
 use diesel::debug_query;
 use diesel::prelude::*;
 use diesel::r2d2::{self, ConnectionManager};
@@ -83,6 +84,20 @@ pub fn get_latest_files<C: Connection<Backend = Sqlite>>(
     Ok(matches)
 }
 
+pub fn file_update_mtime<C: Connection<Backend = Sqlite>>(
+    connection: &C,
+    file_id: i32,
+    m_time: Option<NaiveDateTime>,
+) -> Result<usize> {
+    use crate::database::inner::schema::files::dsl::*;
+
+    debug!("Setting file ID {}'s mtime = {:?}", file_id, m_time);
+
+    Ok(diesel::update(files.filter(id.eq(file_id)))
+        .set(mtime.eq(m_time))
+        .execute(connection)?)
+}
+
 pub fn file_set_valid<C: Connection<Backend = Sqlite>>(
     connection: &C,
     file_id: i32,
diff --git a/src/filesystem.rs b/src/filesystem.rs
index 7601e71..c900325 100644
--- a/src/filesystem.rs
+++ b/src/filesystem.rs
@@ -12,7 +12,8 @@ use crate::database::entry::{Entry, EntryValue, InvariantEntry};
 use crate::database::hierarchies::{resolve_path_cached, ResolveCache, UNode, UPath};
 use crate::database::inner::models;
 use crate::database::{
-    file_set_valid, insert_entry, insert_file, retrieve_all_files, DbPool, UPEND_SUBDIR,
+    file_set_valid, file_update_mtime, insert_entry, insert_file, retrieve_all_files, DbPool,
+    UPEND_SUBDIR,
 };
 use crate::util::hash::{Hash, Hashable};
 use crate::util::jobs::{Job, JobContainer, JobId, State};
@@ -254,18 +255,24 @@ fn _process_directory_entry<P: AsRef<Path>>(
         let existing_file = existing_file.clone();
         drop(existing_files_read);
 
-        let mut same = size == existing_file.size && mtime == existing_file.mtime;
-        if !same {
-            file_hash = Some(path.hash()?);
-            same = file_hash.as_ref().unwrap() == &existing_file.hash;
-        }
+        if size == existing_file.size {
+            let same_mtime = mtime.is_some() && mtime == existing_file.mtime;
+            let mut same_hash = false;
 
-        if same {
-            if !existing_file.valid {
-                file_set_valid(connection, existing_file.id, true)?;
+            if !same_mtime {
+                file_hash = Some(path.hash()?);
+                same_hash = file_hash.as_ref().unwrap() == &existing_file.hash;
             }
 
-            {
+            if same_mtime || same_hash {
+                if mtime != existing_file.mtime {
+                    file_update_mtime(connection, existing_file.id, mtime)?;
+                }
+
+                if !existing_file.valid {
+                    file_set_valid(connection, existing_file.id, true)?;
+                }
+
                 let mut existing_files_write = existing_files.write().unwrap();
                 let maybe_existing_file = existing_files_write
                     .iter()