diff --git a/libc/malloc_debug/PointerData.cpp b/libc/malloc_debug/PointerData.cpp
index 638061b..6e9d24f 100644
--- a/libc/malloc_debug/PointerData.cpp
+++ b/libc/malloc_debug/PointerData.cpp
@@ -266,12 +266,12 @@
   error_log("  hash_index %zu does not have matching frame data.", hash_index);
 }
 
-void PointerData::LogFreeError(const FreePointerInfoType& info, size_t usable_size) {
+void PointerData::LogFreeError(const FreePointerInfoType& info, size_t max_cmp_bytes) {
   error_log(LOG_DIVIDER);
   uint8_t* memory = reinterpret_cast<uint8_t*>(info.pointer);
   error_log("+++ ALLOCATION %p USED AFTER FREE", memory);
   uint8_t fill_free_value = g_debug->config().fill_free_value();
-  for (size_t i = 0; i < usable_size; i++) {
+  for (size_t i = 0; i < max_cmp_bytes; i++) {
     if (memory[i] != fill_free_value) {
       error_log("  allocation[%zu] = 0x%02x (expected 0x%02x)", i, memory[i], fill_free_value);
     }
@@ -314,11 +314,12 @@
   size_t bytes = (usable_size < g_debug->config().fill_on_free_bytes())
                      ? usable_size
                      : g_debug->config().fill_on_free_bytes();
+  size_t max_cmp_bytes = bytes;
   const uint8_t* memory = reinterpret_cast<const uint8_t*>(info.pointer);
   while (bytes > 0) {
     size_t bytes_to_cmp = (bytes < g_cmp_mem.size()) ? bytes : g_cmp_mem.size();
     if (memcmp(memory, g_cmp_mem.data(), bytes_to_cmp) != 0) {
-      LogFreeError(info, usable_size);
+      LogFreeError(info, max_cmp_bytes);
     }
     bytes -= bytes_to_cmp;
     memory = &memory[bytes_to_cmp];
diff --git a/libc/malloc_debug/tests/malloc_debug_unit_tests.cpp b/libc/malloc_debug/tests/malloc_debug_unit_tests.cpp
index 44f9795..6da95ca 100644
--- a/libc/malloc_debug/tests/malloc_debug_unit_tests.cpp
+++ b/libc/malloc_debug/tests/malloc_debug_unit_tests.cpp
@@ -990,6 +990,35 @@
   ASSERT_STREQ("", getFakeLogPrint().c_str());
 }
 
+TEST_F(MallocDebugTest, free_track_pointer_modified_after_free) {
+  Init("free_track=4 fill_on_free=2 free_track_backtrace_num_frames=0");
+
+  void* pointers[5];
+  for (size_t i = 0; i < sizeof(pointers) / sizeof(void*); i++) {
+    pointers[i] = debug_malloc(100);
+    ASSERT_TRUE(pointers[i] != nullptr);
+    memset(pointers[i], 0, 100);
+  }
+
+  debug_free(pointers[0]);
+
+  // overwrite the whole pointer, only expect errors on the fill bytes we check.
+  memset(pointers[0], 0x20, 100);
+
+  for (size_t i = 1; i < sizeof(pointers) / sizeof(void*); i++) {
+    debug_free(pointers[i]);
+  }
+
+  std::string expected_log(DIVIDER);
+  expected_log += android::base::StringPrintf("6 malloc_debug +++ ALLOCATION %p USED AFTER FREE\n",
+                                              pointers[0]);
+  expected_log += "6 malloc_debug   allocation[0] = 0x20 (expected 0xef)\n";
+  expected_log += "6 malloc_debug   allocation[1] = 0x20 (expected 0xef)\n";
+  expected_log += DIVIDER;
+  ASSERT_STREQ("", getFakeLogBuf().c_str());
+  ASSERT_STREQ(expected_log.c_str(), getFakeLogPrint().c_str());
+}
+
 TEST_F(MallocDebugTest, get_malloc_leak_info_invalid) {
   Init("fill");