diff --git a/CHANGELOG.md b/CHANGELOG.md
index f53758e3f..dd3ede7c6 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -414,6 +414,11 @@
 
 ### Bug fixes
 
+- Fixed a bug where the generated Erlang `.app` file's `modules` list would only
+  contain the modules recompiled by the latest build, becoming empty on a warm
+  rebuild where nothing changed.
+  ([Charlie Tonneslan](https://github.com/c-tonneslan))
+
 - When using the language server to extract a function from within an anonymous
   function, the return value of the extracted function is respected.
 
diff --git a/compiler-core/src/build/package_compiler.rs b/compiler-core/src/build/package_compiler.rs
index 68c11a34e..9a1d43e14 100644
--- a/compiler-core/src/build/package_compiler.rs
+++ b/compiler-core/src/build/package_compiler.rs
@@ -239,7 +239,7 @@ where
         //     modules
         // };
 
-        if let Err(error) = self.perform_codegen(&modules) {
+        if let Err(error) = self.perform_codegen(&modules, &cached_module_names) {
             return error.into();
         }
 
@@ -352,7 +352,11 @@ where
         Ok(())
     }
 
-    fn perform_codegen(&mut self, modules: &[Module]) -> Result<()> {
+    fn perform_codegen(
+        &mut self,
+        modules: &[Module],
+        cached_module_names: &[EcoString],
+    ) -> Result<()> {
         if !self.perform_codegen {
             tracing::debug!("skipping_codegen");
             return Ok(());
@@ -370,7 +374,7 @@ where
                 prelude_location,
             ),
             TargetCodegenConfiguration::Erlang { app_file } => {
-                self.perform_erlang_codegen(modules, app_file.as_ref())
+                self.perform_erlang_codegen(modules, cached_module_names, app_file.as_ref())
             }
         }
     }
@@ -378,6 +382,7 @@ where
     fn perform_erlang_codegen(
         &mut self,
         modules: &[Module],
+        cached_module_names: &[EcoString],
         app_file_config: Option<&ErlangAppCodegenConfiguration>,
     ) -> Result<(), Error> {
         let mut written = HashSet::new();
@@ -418,6 +423,7 @@ where
                 io,
                 &self.config,
                 modules,
+                cached_module_names,
                 native_modules,
             )?;
         }
diff --git a/compiler-core/src/codegen.rs b/compiler-core/src/codegen.rs
index 2601e11b0..26ec89fd3 100644
--- a/compiler-core/src/codegen.rs
+++ b/compiler-core/src/codegen.rs
@@ -99,6 +99,7 @@ impl<'a> ErlangApp<'a> {
         writer: Writer,
         config: &PackageConfig,
         modules: &[Module],
+        cached_module_names: &[EcoString],
         native_modules: Vec<EcoString>,
     ) -> Result<()> {
         fn tuple(key: &str, value: &str) -> String {
@@ -119,9 +120,12 @@ impl<'a> ErlangApp<'a> {
             }
         };
 
+        // Include the cached modules that were not recompiled this build, so a
+        // warm rebuild doesn't shrink the `modules` list (see #5834).
         let modules = modules
             .iter()
             .map(|m| m.erlang_name())
+            .chain(cached_module_names.iter().map(module_erlang_name))
             .chain(native_modules)
             .unique()
             .sorted()
@@ -298,3 +302,40 @@ impl<'a> JavaScript<'a> {
         Ok(())
     }
 }
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use crate::io::{FileSystemReader, memory::InMemoryFileSystem};
+    use std::collections::HashMap;
+
+    #[test]
+    fn app_file_includes_cached_modules() {
+        // A warm rebuild recompiles nothing, so every module arrives as a cached
+        // name rather than in `modules`; they must still be listed in the .app
+        // (https://github.com/gleam-lang/gleam/issues/5834).
+        let fs = InMemoryFileSystem::new();
+        let mut config = PackageConfig::default();
+        config.name = "my_app".into();
+        let codegen_config = ErlangAppCodegenConfiguration {
+            include_dev_deps: false,
+            package_name_overrides: HashMap::new(),
+        };
+
+        ErlangApp::new(Utf8Path::new("/ebin"), &codegen_config)
+            .render(
+                fs.clone(),
+                &config,
+                &[],
+                &["my_app/one".into(), "my_app/two".into()],
+                vec![],
+            )
+            .expect("render .app");
+
+        let app = fs
+            .read(Utf8Path::new("/ebin/my_app.app"))
+            .expect("read .app");
+        assert!(app.contains("my_app@one"), "{app}");
+        assert!(app.contains("my_app@two"), "{app}");
+    }
+}