diff --git a/build.rs b/build.rs
index b1cfaa97..94d2f89e 100644
--- a/build.rs
+++ b/build.rs
@@ -2,6 +2,10 @@
 use std::process::Command;
 
 fn main() {
+    if let Ok(hash) = std::env::var("SOURCE_GIT_HASH") {
+        println!("cargo:rustc-env=GIT_HASH={}", hash);
+        return;
+    }
     if let Ok(output) = Command::new("git").args(["rev-parse", "HEAD"]).output() {
         let git_hash = String::from_utf8(output.stdout).unwrap();
         println!("cargo:rustc-env=GIT_HASH={}", git_hash);