diff --git a/build.rs b/build.rs
index 3a8149e..2bf0bd2 100644
--- a/build.rs
+++ b/build.rs
@@ -1,3 +1,16 @@
+use std::process::Command;
+
 fn main() {
     println!("cargo:rerun-if-changed=migrations");
+
+    let git_short_hash = Command::new("git")
+        .args(["rev-parse", "--short", "HEAD"])
+        .output()
+        .ok()
+        .and_then(|o| String::from_utf8(o.stdout).ok())
+        .map(|s| s.trim().to_string())  // Trim newline
+        .unwrap_or_else(|| "UNKNOWN".to_string());
+
+    // Tell Cargo to set `GIT_SHORT_HASH` for the main compilation
+    println!("cargo:rustc-env=GIT_SHORT_HASH={}", git_short_hash);
 }
diff --git a/src/api/v1/stats.rs b/src/api/v1/stats.rs
index bf2bec3..30888aa 100644
--- a/src/api/v1/stats.rs
+++ b/src/api/v1/stats.rs
@@ -12,6 +12,7 @@ use crate::error::Error;
 use crate::schema::users::dsl::{users, uuid};
 
 const VERSION: Option<&'static str> = option_env!("CARGO_PKG_VERSION");
+const GIT_SHORT_HASH: &str = env!("GIT_SHORT_HASH");
 
 #[derive(Serialize)]
 struct Response {
@@ -57,7 +58,7 @@ pub async fn res(data: web::Data<Data>) -> Result<HttpResponse, Error> {
         registration_enabled: data.config.instance.registration,
         email_verification_required: data.config.instance.require_email_verification,
         // TODO: Get build number from git hash or remove this from the spec
-        build_number: String::from("how do i implement this?"),
+        build_number: String::from(GIT_SHORT_HASH),
     };
 
     Ok(HttpResponse::Ok().json(response))