diff --git a/CHANGELOG.md b/CHANGELOG.md
index c731e29b1..464b981b0 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -99,6 +99,9 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 * `jj log` now accepts a `--reversed` option, which will show older commits
   first.
 
+* The "(no name/email configured)" placeholder value for name/email will now be
+  replaced if once you modify a commit after having configured your name/email.
+
 ### Fixed bugs
 
 * When rebasing a conflict where one side modified a file and the other side
diff --git a/lib/src/commit_builder.rs b/lib/src/commit_builder.rs
index f20273918..df20183c4 100644
--- a/lib/src/commit_builder.rs
+++ b/lib/src/commit_builder.rs
@@ -66,6 +66,14 @@ impl CommitBuilder {
         let mut commit = predecessor.store_commit().clone();
         commit.predecessors = vec![predecessor.id().clone()];
         commit.committer = settings.signature();
+        // If the user had not configured a name and email before but now they have,
+        // update the the author fields with the new information.
+        if commit.author.name == UserSettings::user_name_placeholder() {
+            commit.author.name = commit.committer.name.clone();
+        }
+        if commit.author.email == UserSettings::user_email_placeholder() {
+            commit.author.email = commit.committer.email.clone();
+        }
         CommitBuilder {
             store: store.clone(),
             commit,
diff --git a/lib/src/settings.rs b/lib/src/settings.rs
index 062efa7c7..cd2d0f83b 100644
--- a/lib/src/settings.rs
+++ b/lib/src/settings.rs
@@ -56,13 +56,21 @@ impl UserSettings {
     pub fn user_name(&self) -> String {
         self.config
             .get_string("user.name")
-            .unwrap_or_else(|_| "(no name configured)".to_string())
+            .unwrap_or_else(|_| Self::user_name_placeholder().to_string())
+    }
+
+    pub fn user_name_placeholder() -> &'static str {
+        "(no name configured)"
     }
 
     pub fn user_email(&self) -> String {
         self.config
             .get_string("user.email")
-            .unwrap_or_else(|_| "(no email configured)".to_string())
+            .unwrap_or_else(|_| Self::user_email_placeholder().to_string())
+    }
+
+    pub fn user_email_placeholder() -> &'static str {
+        "(no email configured)"
     }
 
     pub fn push_branch_prefix(&self) -> String {
diff --git a/lib/tests/test_commit_builder.rs b/lib/tests/test_commit_builder.rs
index 607e39b79..c958fab89 100644
--- a/lib/tests/test_commit_builder.rs
+++ b/lib/tests/test_commit_builder.rs
@@ -153,6 +153,52 @@ fn test_rewrite(use_git: bool) {
     );
 }
 
+// An author field with the placeholder name/email should get filled in on
+// rewrite
+#[test_case(false ; "local backend")]
+#[test_case(true ; "git backend")]
+fn test_rewrite_update_missing_user(use_git: bool) {
+    let missing_user_settings =
+        UserSettings::from_config(config::Config::builder().build().unwrap());
+    let test_repo = TestRepo::init(use_git);
+    let repo = &test_repo.repo;
+    let store = repo.store().clone();
+
+    let mut tx = repo.start_transaction("test");
+    let initial_commit = CommitBuilder::for_new_commit(
+        &missing_user_settings,
+        &store,
+        repo.store().empty_tree_id().clone(),
+    )
+    .write_to_repo(tx.mut_repo());
+    assert_eq!(initial_commit.author().name, "(no name configured)");
+    assert_eq!(initial_commit.author().email, "(no email configured)");
+    assert_eq!(initial_commit.committer().name, "(no name configured)");
+    assert_eq!(initial_commit.committer().email, "(no email configured)");
+
+    let config = config::Config::builder()
+        .set_override("user.name", "Configured User")
+        .unwrap()
+        .set_override("user.email", "configured.user@example.com")
+        .unwrap()
+        .build()
+        .unwrap();
+    let settings = UserSettings::from_config(config);
+    let rewritten_commit = CommitBuilder::for_rewrite_from(&settings, &store, &initial_commit)
+        .write_to_repo(tx.mut_repo());
+
+    assert_eq!(rewritten_commit.author().name, "Configured User");
+    assert_eq!(
+        rewritten_commit.author().email,
+        "configured.user@example.com"
+    );
+    assert_eq!(rewritten_commit.committer().name, "Configured User");
+    assert_eq!(
+        rewritten_commit.committer().email,
+        "configured.user@example.com"
+    );
+}
+
 #[test_case(false ; "local backend")]
 // #[test_case(true ; "git backend")]
 fn test_commit_builder_descendants(use_git: bool) {