diff --git a/src/broadcaster.zig b/src/broadcaster.zig
--- a/src/broadcaster.zig
+++ b/src/broadcaster.zig
@@ -683,7 +683,9 @@
     } else |_| {}
 
     // glibc malloc arena stats — distinguishes in-use heap from fragmentation
-    const mi = malloc_h.mallinfo2();
+    // uses mallinfo (not mallinfo2) for older glibc compat; int fields cap at 2 GiB
+    // but that's enough to distinguish leak vs fragmentation patterns
+    const mi = malloc_h.mallinfo();
     std.fmt.format(w,
         \\# TYPE relay_malloc_arena_bytes gauge
         \\# HELP relay_malloc_arena_bytes total bytes claimed from OS by malloc