diff --git a/src/deb/mod.rs b/src/deb/mod.rs
index 0dfc160..c051a8b 100644
--- a/src/deb/mod.rs
+++ b/src/deb/mod.rs
@@ -83,8 +83,20 @@ async fn build_binary_package_impl(
     let changelog_path = cwd.join("debian/changelog");
     let (package, version, package_series) =
         crate::changelog::parse_changelog_header(&changelog_path)?;
+    // UNRELEASED is not a real archive series: without an explicit --series,
+    // build against the development series of the host vendor's distribution
+    // instead. An explicit --series always wins.
+    let resolved_series;
     let series = if let Some(s) = series {
         s
+    } else if crate::distro_info::is_unreleased(&package_series) {
+        let dist = crate::build::env::current_vendor();
+        resolved_series = crate::distro_info::effective_series(&package_series, &dist).await?;
+        log::info!(
+            "Changelog is UNRELEASED, building against series {}",
+            resolved_series
+        );
+        resolved_series.as_str()
     } else {
         &package_series
     };
diff --git a/src/distro_info.rs b/src/distro_info.rs
index 845e490..94b88e3 100644
--- a/src/distro_info.rs
+++ b/src/distro_info.rs
@@ -169,6 +169,16 @@ pub fn supported_dists() -> Vec<String> {
     DATA.dist.keys().cloned().collect()
 }
 
+/// Special changelog distribution marking an entry that has not been
+/// released to any archive series yet
+pub const UNRELEASED: &str = "UNRELEASED";
+
+/// Whether `series` is the special [`UNRELEASED`] distribution rather than
+/// a real archive series
+pub fn is_unreleased(series: &str) -> bool {
+    series == UNRELEASED
+}
+
 /// Get time-ordered list of series information for a distribution, development series first
 pub async fn get_ordered_series(dist: &str) -> Result<Vec<SeriesInformation>, Box<dyn Error>> {
     let dist_data = DATA.dist.get(dist).ok_or_else(|| {
@@ -206,6 +216,24 @@ pub async fn get_ordered_series_name(dist: &str) -> Result<Vec<String>, Box<dyn
     Ok(series.iter().map(|info| info.series.clone()).collect())
 }
 
+/// The series to actually target when the changelog says [`UNRELEASED`]:
+/// the development series of `dist`, i.e. the first entry of
+/// [`get_ordered_series_name`] (which is documented "development series
+/// first"). UNRELEASED work conventionally targets the next release, not
+/// the last stable one. Any other `series` is returned unchanged. Errors
+/// when `dist` is unknown or has no series list.
+pub async fn effective_series(series: &str, dist: &str) -> Result<String, Box<dyn Error>> {
+    if !is_unreleased(series) {
+        return Ok(series.to_string());
+    }
+
+    get_ordered_series_name(dist)
+        .await?
+        .into_iter()
+        .next()
+        .ok_or_else(|| format!("Distribution '{}' has no series to target", dist).into())
+}
+
 /// Get the latest released series for a dist (excluding future releases and special cases like sid)
 pub async fn get_latest_released_series(dist: &str) -> Result<String, Box<dyn Error>> {
     let latest = get_n_latest_released_series(dist, 1).await?;
@@ -523,6 +551,52 @@ mod tests {
         );
     }
 
+    #[test]
+    fn test_is_unreleased() {
+        // Matching is exact: UNRELEASED is uppercase by Debian convention
+        assert!(is_unreleased("UNRELEASED"));
+        assert!(!is_unreleased("unreleased"));
+        assert!(!is_unreleased("noble"));
+        assert!(!is_unreleased(""));
+    }
+
+    #[tokio::test]
+    async fn test_effective_series_passthrough() {
+        // A real series is returned unchanged, and the dist is not even
+        // looked up (an unknown dist only matters for UNRELEASED)
+        assert_eq!(effective_series("noble", "ubuntu").await.unwrap(), "noble");
+        assert_eq!(effective_series("sid", "debian").await.unwrap(), "sid");
+        assert_eq!(
+            effective_series("noble", "unknown-distro").await.unwrap(),
+            "noble"
+        );
+    }
+
+    #[tokio::test]
+    async fn test_effective_series_unreleased() {
+        // UNRELEASED resolves to the development series of the dist, i.e.
+        // the first entry of the time-ordered list. On current distro-info
+        // data this is the next Ubuntu release, while Debian's list starts
+        // with 'experimental' (sid comes second), so assert against the
+        // data itself rather than a hardcoded name.
+        for dist in ["ubuntu", "debian"] {
+            let ordered = get_ordered_series_name(dist).await.unwrap();
+            let resolved = effective_series(UNRELEASED, dist).await.unwrap();
+            assert_eq!(resolved, ordered[0]);
+            assert_ne!(resolved, UNRELEASED);
+        }
+    }
+
+    #[tokio::test]
+    async fn test_effective_series_unknown_dist() {
+        // UNRELEASED on an unknown distribution cannot be resolved
+        assert!(
+            effective_series(UNRELEASED, "unknown-distro")
+                .await
+                .is_err()
+        );
+    }
+
     #[tokio::test]
     async fn test_get_debian_series() {
         let series = get_ordered_series_name("debian").await.unwrap();
diff --git a/src/main.rs b/src/main.rs
index 2a68a73..6c245b5 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -198,14 +198,39 @@ fn main() {
                 let changelog_path = cwd.join("debian/changelog");
                 match pkh::changelog::parse_changelog_header(&changelog_path) {
                     Ok((_pkg, _ver, current_series)) => {
-                        // Try to get the list of available series for this distribution
+                        // UNRELEASED is not a real series: offer it as a
+                        // pinned first entry (selecting it keeps the changelog
+                        // unreleased) on top of the current vendor's series
+                        // list, defaulting to the development series. Any
+                        // other series resolves through the series list of
+                        // its own distribution.
                         match rt.block_on(async {
-                            let dist =
-                                pkh::distro_info::get_dist_from_series(&current_series).await?;
-                            pkh::distro_info::get_ordered_series_name(&dist).await
+                            if pkh::distro_info::is_unreleased(&current_series) {
+                                let dist = pkh::build::env::current_vendor();
+                                let mut series_list =
+                                    vec![pkh::distro_info::UNRELEASED.to_string()];
+                                series_list.extend(
+                                    pkh::distro_info::get_ordered_series_name(&dist).await?,
+                                );
+                                Ok(series_list)
+                            } else {
+                                let dist =
+                                    pkh::distro_info::get_dist_from_series(&current_series).await?;
+                                pkh::distro_info::get_ordered_series_name(&dist).await
+                            }
                         }) {
                             Ok(series_list) => {
-                                match pkh::ui::select_series(&series_list, &current_series) {
+                                // Default to the development series (the
+                                // first real entry) when the changelog is
+                                // UNRELEASED, not to the pinned entry itself
+                                let default = if pkh::distro_info::is_unreleased(&current_series)
+                                    && series_list.len() > 1
+                                {
+                                    series_list[1].clone()
+                                } else {
+                                    current_series.clone()
+                                };
+                                match pkh::ui::select_series(&series_list, &default) {
                                     Ok(selected) => Some(selected),
                                     Err(e) => {
                                         error!(