diff --git a/CHANGELOG.md b/CHANGELOG.md
index d5c2692d..6618b9c8 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,6 +1,10 @@
 # Rojo Changelog
 
 ## [Unreleased]
+* Changed default project file name from `roblox-project.json` to `default.project.json` ([#120](https://github.com/LPGhatguy/rojo/pull/120))
+    * The old file name will still be supported until 0.5.0 is fully released.
+* Added warning when loading project files that don't end in `.project.json`
+    * This new extension enables Rojo to distinguish project files from random JSON files, which is necessary to support nested projects.
 * Added new (empty) diagnostic page served from the server
 * Added better error messages for when a file is missing that's referenced by a Rojo project
 * Added support for visualization endpoints returning GraphViz source when Dot is not available
diff --git a/plugin/roblox-project.json b/plugin/default.project.json
similarity index 100%
rename from plugin/roblox-project.json
rename to plugin/default.project.json
diff --git a/plugin/place-project.json b/plugin/place.project.json
similarity index 100%
rename from plugin/place-project.json
rename to plugin/place.project.json
diff --git a/server/src/commands/build.rs b/server/src/commands/build.rs
index e5880aea..2c839e69 100644
--- a/server/src/commands/build.rs
+++ b/server/src/commands/build.rs
@@ -79,6 +79,7 @@ pub fn build(options: &BuildOptions) -> Result<(), BuildError> {
     info!("Looking for project at {}", options.fuzzy_project_path.display());
 
     let project = Project::load_fuzzy(&options.fuzzy_project_path)?;
+    project.check_compatibility();
 
     info!("Found project at {}", project.file_location.display());
     info!("Using project {:#?}", project);
diff --git a/server/src/commands/serve.rs b/server/src/commands/serve.rs
index 9b2db9dd..58c0d16e 100644
--- a/server/src/commands/serve.rs
+++ b/server/src/commands/serve.rs
@@ -39,6 +39,7 @@ pub fn serve(options: &ServeOptions) -> Result<(), ServeError> {
     info!("Looking for project at {}", options.fuzzy_project_path.display());
 
     let project = Arc::new(Project::load_fuzzy(&options.fuzzy_project_path)?);
+    project.check_compatibility();
 
     info!("Found project at {}", project.file_location.display());
     info!("Using project {:#?}", project);
diff --git a/server/src/commands/upload.rs b/server/src/commands/upload.rs
index 0498693c..fb26e0ab 100644
--- a/server/src/commands/upload.rs
+++ b/server/src/commands/upload.rs
@@ -60,6 +60,7 @@ pub fn upload(options: &UploadOptions) -> Result<(), UploadError> {
     info!("Looking for project at {}", options.fuzzy_project_path.display());
 
     let project = Project::load_fuzzy(&options.fuzzy_project_path)?;
+    project.check_compatibility();
 
     info!("Found project at {}", project.file_location.display());
     info!("Using project {:#?}", project);
diff --git a/server/src/project.rs b/server/src/project.rs
index e6c1509c..c391e02d 100644
--- a/server/src/project.rs
+++ b/server/src/project.rs
@@ -6,12 +6,14 @@ use std::{
     path::{Path, PathBuf},
 };
 
+use log::warn;
 use failure::Fail;
 use maplit::hashmap;
 use rbx_tree::RbxValue;
 use serde_derive::{Serialize, Deserialize};
 
-pub static PROJECT_FILENAME: &'static str = "roblox-project.json";
+pub static PROJECT_FILENAME: &'static str = "default.project.json";
+pub static COMPAT_PROJECT_FILENAME: &'static str = "roblox-project.json";
 
 // Methods used for Serde's default value system, which doesn't support using
 // value literals directly, only functions that return values.
@@ -362,11 +364,17 @@ impl Project {
         } else if location_metadata.is_dir() {
             let with_file = start_location.join(PROJECT_FILENAME);
 
-            if let Ok(with_file_metadata) = fs::metadata(&with_file) {
-                if with_file_metadata.is_file() {
+            if let Ok(file_metadata) = fs::metadata(&with_file) {
+                if file_metadata.is_file() {
                     return Some(with_file);
-                } else {
-                    return None;
+                }
+            }
+
+            let with_compat_file = start_location.join(COMPAT_PROJECT_FILENAME);
+
+            if let Ok(file_metadata) = fs::metadata(&with_compat_file) {
+                if file_metadata.is_file() {
+                    return Some(with_compat_file);
                 }
             }
         }
@@ -405,6 +413,25 @@ impl Project {
         Ok(())
     }
 
+    /// Checks if there are any compatibility issues with this project file and
+    /// warns the user if there are any.
+    pub fn check_compatibility(&self) {
+        let file_name = self.file_location
+            .file_name().unwrap()
+            .to_str().expect("Project file path was not valid Unicode!");
+
+        if file_name == COMPAT_PROJECT_FILENAME {
+            warn!("Rojo's default project file name changed in 0.5.0-alpha3.");
+            warn!("Support for the old project file name will be dropped before 0.5.0 releases.");
+            warn!("Your project file is named {}", COMPAT_PROJECT_FILENAME);
+            warn!("Rename your project file to {}", PROJECT_FILENAME);
+        } else if !file_name.ends_with(".project.json") {
+            warn!("Starting in Rojo 0.5.0-alpha3, it's recommended to give all project files the");
+            warn!(".project.json extension. This helps Rojo differentiate project files from");
+            warn!("other JSON files!");
+        }
+    }
+
     fn to_source_project(&self) -> SourceProject {
         SourceProject {
             name: self.name.clone(),
diff --git a/server/tests/read_projects.rs b/server/tests/read_projects.rs
index af30ed99..55ae5550 100644
--- a/server/tests/read_projects.rs
+++ b/server/tests/read_projects.rs
@@ -21,7 +21,7 @@ lazy_static! {
 
 #[test]
 fn empty() {
-    let project_file_location = TEST_PROJECTS_ROOT.join("empty/roblox-project.json");
+    let project_file_location = TEST_PROJECTS_ROOT.join("empty/default.project.json");
     let project = Project::load_exact(&project_file_location).unwrap();
 
     assert_eq!(project.name, "empty");
@@ -29,7 +29,7 @@ fn empty() {
 
 #[test]
 fn empty_fuzzy_file() {
-    let project_file_location = TEST_PROJECTS_ROOT.join("empty/roblox-project.json");
+    let project_file_location = TEST_PROJECTS_ROOT.join("empty/default.project.json");
     let project = Project::load_fuzzy(&project_file_location).unwrap();
 
     assert_eq!(project.name, "empty");
@@ -45,7 +45,7 @@ fn empty_fuzzy_folder() {
 
 #[test]
 fn single_sync_point() {
-    let project_file_location = TEST_PROJECTS_ROOT.join("single-sync-point/roblox-project.json");
+    let project_file_location = TEST_PROJECTS_ROOT.join("single-sync-point/default.project.json");
     let project = Project::load_exact(&project_file_location).unwrap();
 
     let expected_project = {
@@ -100,7 +100,7 @@ fn single_sync_point() {
 
 #[test]
 fn test_model() {
-    let project_file_location = TEST_PROJECTS_ROOT.join("test-model/roblox-project.json");
+    let project_file_location = TEST_PROJECTS_ROOT.join("test-model/default.project.json");
     let project = Project::load_exact(&project_file_location).unwrap();
 
     assert_eq!(project.name, "test-model");
diff --git a/test-projects/composing-models/roblox-project.json b/test-projects/composing-models/default.project.json
similarity index 100%
rename from test-projects/composing-models/roblox-project.json
rename to test-projects/composing-models/default.project.json
diff --git a/test-projects/empty/roblox-project.json b/test-projects/empty/default.project.json
similarity index 100%
rename from test-projects/empty/roblox-project.json
rename to test-projects/empty/default.project.json
diff --git a/test-projects/missing-files/roblox-project.json b/test-projects/missing-files/default.project.json
similarity index 100%
rename from test-projects/missing-files/roblox-project.json
rename to test-projects/missing-files/default.project.json
diff --git a/test-projects/single-sync-point/roblox-project.json b/test-projects/single-sync-point/default.project.json
similarity index 100%
rename from test-projects/single-sync-point/roblox-project.json
rename to test-projects/single-sync-point/default.project.json
diff --git a/test-projects/test-model/roblox-project.json b/test-projects/test-model/default.project.json
similarity index 100%
rename from test-projects/test-model/roblox-project.json
rename to test-projects/test-model/default.project.json