diff --git a/os2-ref/build.rs b/os2-ref/build.rs
index 4a44c565f..9d0333eb9 100644
--- a/os2-ref/build.rs
+++ b/os2-ref/build.rs
@@ -36,7 +36,9 @@ _num_app:
     for i in 0..apps.len() {
         writeln!(f, r#"    .quad app_{}_start"#, i)?;
     }
-    writeln!(f, r#"    .quad app_{}_end"#, apps.len() - 1)?;
+    if !apps.is_empty() {
+        writeln!(f, r#"    .quad app_{}_end"#, apps.len() - 1)?;
+    }
 
     for (idx, app) in apps.iter().enumerate() {
         println!("app_{}: {}", idx, app);
diff --git a/os3-ref/build.rs b/os3-ref/build.rs
index 92953d58b..d18a881fb 100644
--- a/os3-ref/build.rs
+++ b/os3-ref/build.rs
@@ -39,7 +39,9 @@ _num_app:
     for i in 0..apps.len() {
         writeln!(f, r#"    .quad app_{}_start"#, i)?;
     }
-    writeln!(f, r#"    .quad app_{}_end"#, apps.len() - 1)?;
+    if !apps.is_empty() {
+        writeln!(f, r#"    .quad app_{}_end"#, apps.len() - 1)?;
+    }
 
     for (idx, app) in apps.iter().enumerate() {
         println!("app_{}: {}", idx, app);
diff --git a/os4-ref/build.rs b/os4-ref/build.rs
index 63845c730..ca43ba7ae 100644
--- a/os4-ref/build.rs
+++ b/os4-ref/build.rs
@@ -39,7 +39,9 @@ _num_app:
     for i in 0..apps.len() {
         writeln!(f, r#"    .quad app_{}_start"#, i)?;
     }
-    writeln!(f, r#"    .quad app_{}_end"#, apps.len() - 1)?;
+    if !apps.is_empty() {
+        writeln!(f, r#"    .quad app_{}_end"#, apps.len() - 1)?;
+    }
 
     for (idx, app) in apps.iter().enumerate() {
         println!("app_{}: {}", idx, app);
diff --git a/os5-ref/build.rs b/os5-ref/build.rs
index d333f8c29..bc5406d9b 100644
--- a/os5-ref/build.rs
+++ b/os5-ref/build.rs
@@ -40,7 +40,9 @@ _num_app:
     for i in 0..apps.len() {
         writeln!(f, r#"    .quad app_{}_start"#, i)?;
     }
-    writeln!(f, r#"    .quad app_{}_end"#, apps.len() - 1)?;
+    if !apps.is_empty() {
+        writeln!(f, r#"    .quad app_{}_end"#, apps.len() - 1)?;
+    }
 
     writeln!(
         f,