diff --git a/libc/malloc_debug/backtrace.cpp b/libc/malloc_debug/backtrace.cpp
index 18ce8b8..75a255c 100644
--- a/libc/malloc_debug/backtrace.cpp
+++ b/libc/malloc_debug/backtrace.cpp
@@ -142,6 +142,8 @@
     if (dladdr(reinterpret_cast<void*>(frames[frame_num]), &info) != 0) {
       offset = reinterpret_cast<uintptr_t>(info.dli_saddr);
       symbol = info.dli_sname;
+    } else {
+      info.dli_fname = nullptr;
     }
 
     uintptr_t rel_pc = offset;