diff --git a/libc/malloc_debug/backtrace.cpp b/libc/malloc_debug/backtrace.cpp
index ecb3a80..6a32fca 100644
--- a/libc/malloc_debug/backtrace.cpp
+++ b/libc/malloc_debug/backtrace.cpp
@@ -50,7 +50,7 @@
 typedef struct _Unwind_Context __unwind_context;
 
 static MapData g_map_data;
-static const MapEntry* g_current_code_map = nullptr;
+static MapEntry g_current_code_map;
 
 static _Unwind_Reason_Code find_current_map(__unwind_context* context, void*) {
   uintptr_t ip = _Unwind_GetIP(context);
@@ -58,11 +58,15 @@
   if (ip == 0) {
     return _URC_END_OF_STACK;
   }
-  g_current_code_map = g_map_data.find(ip);
+  auto map = g_map_data.find(ip);
+  if (map != nullptr) {
+    g_current_code_map = *map;
+  }
   return _URC_END_OF_STACK;
 }
 
 void backtrace_startup() {
+  g_map_data.ReadMaps();
   _Unwind_Backtrace(find_current_map, nullptr);
 }
 
@@ -98,7 +102,8 @@
   }
 
   // Do not record the frames that fall in our own shared library.
-  if (g_current_code_map && (ip >= g_current_code_map->start) && ip < g_current_code_map->end) {
+  if (g_current_code_map.start() != 0 && (ip >= g_current_code_map.start()) &&
+      ip < g_current_code_map.end()) {
     return _URC_NO_REASON;
   }
 
@@ -113,6 +118,10 @@
 }
 
 std::string backtrace_string(const uintptr_t* frames, size_t frame_count) {
+  if (g_map_data.NumMaps() == 0) {
+    g_map_data.ReadMaps();
+  }
+
   std::string str;
 
   for (size_t frame_num = 0; frame_num < frame_count; frame_num++) {
@@ -130,14 +139,15 @@
     uintptr_t rel_pc = offset;
     const MapEntry* entry = g_map_data.find(frames[frame_num], &rel_pc);
 
-    const char* soname = (entry != nullptr) ? entry->name.c_str() : info.dli_fname;
+    const char* soname = (entry != nullptr) ? entry->name().c_str() : info.dli_fname;
     if (soname == nullptr) {
       soname = "<unknown>";
     }
 
     char offset_buf[128];
-    if (entry != nullptr && entry->elf_start_offset != 0) {
-      snprintf(offset_buf, sizeof(offset_buf), " (offset 0x%" PRIxPTR ")", entry->elf_start_offset);
+    if (entry != nullptr && entry->elf_start_offset() != 0) {
+      snprintf(offset_buf, sizeof(offset_buf), " (offset 0x%" PRIxPTR ")",
+               entry->elf_start_offset());
     } else {
       offset_buf[0] = '\0';
     }
@@ -167,5 +177,6 @@
 }
 
 void backtrace_log(const uintptr_t* frames, size_t frame_count) {
+  g_map_data.ReadMaps();
   error_log_string(backtrace_string(frames, frame_count).c_str());
 }