diff --git a/artiq/firmware/ksupport/lib.rs b/artiq/firmware/ksupport/lib.rs
index 74ab757ef..c6e747fdb 100644
--- a/artiq/firmware/ksupport/lib.rs
+++ b/artiq/firmware/ksupport/lib.rs
@@ -58,7 +58,7 @@ pub fn panic_fmt(info: &core::panic::PanicInfo) -> ! {
         send(&Log(format_args!("panic at unknown location")));
     }
     if let Some(message) = info.message() {
-        send(&Log(format_args!("{}\n", message)));
+        send(&Log(format_args!(": {}\n", message)));
     } else {
         send(&Log(format_args!("\n")));
     }
diff --git a/artiq/firmware/runtime/main.rs b/artiq/firmware/runtime/main.rs
index d7f983090..d79c7b254 100644
--- a/artiq/firmware/runtime/main.rs
+++ b/artiq/firmware/runtime/main.rs
@@ -309,7 +309,7 @@ pub fn panic_impl(info: &core::panic::PanicInfo) -> ! {
         print!("panic at unknown location");
     }
     if let Some(message) = info.message() {
-        println!("{}", message);
+        println!(": {}", message);
     } else {
         println!("");
     }