diff --git a/src/build/packages.rs b/src/build/packages.rs
index c17be49..edbd1a1 100644
--- a/src/build/packages.rs
+++ b/src/build/packages.rs
@@ -358,8 +358,8 @@ fn flatten_dependencies(dependencies: Vec<Dependency>) -> Vec<Dependency> {
 
 fn make_package(config: config::Config, package_path: &str, is_pinned_dep: bool, is_root: bool) -> Package {
     let source_folders = match config.sources.to_owned() {
-        config::OneOrMore::Single(source) => get_source_dirs(source, None),
-        config::OneOrMore::Multiple(sources) => {
+        Some(config::OneOrMore::Single(source)) => get_source_dirs(source, None),
+        Some(config::OneOrMore::Multiple(sources)) => {
             let mut source_folders: AHashSet<config::PackageSource> = AHashSet::new();
             sources
                 .iter()
@@ -369,6 +369,13 @@ fn make_package(config: config::Config, package_path: &str, is_pinned_dep: bool,
                 .for_each(|source| source_folders.extend(source));
             source_folders
         }
+        None => {
+            if !is_root {
+                log::warn!("Package '{}' has not defined any sources, but is not the root package. This is likely a mistake. It is located: {}", config.name, package_path);
+            }
+
+            AHashSet::new()
+        }
     };
 
     Package {
diff --git a/src/config.rs b/src/config.rs
index 7a6a28f..b242de4 100644
--- a/src/config.rs
+++ b/src/config.rs
@@ -171,7 +171,9 @@ pub type GenTypeConfig = serde_json::Value;
 #[derive(Deserialize, Debug, Clone)]
 pub struct Config {
     pub name: String,
-    pub sources: OneOrMore<Source>,
+    // In the case of monorepos, the root source won't necessarily have to have sources. It can
+    // just be sources in packages
+    pub sources: Option<OneOrMore<Source>>,
     #[serde(rename = "package-specs")]
     pub package_specs: Option<OneOrMore<PackageSpec>>,
     pub warnings: Option<Warnings>,