diff --git a/DevTools/UserspaceEmulator/MallocTracer.cpp b/DevTools/UserspaceEmulator/MallocTracer.cpp
index 1fe405521d..441632826e 100644
--- a/DevTools/UserspaceEmulator/MallocTracer.cpp
+++ b/DevTools/UserspaceEmulator/MallocTracer.cpp
@@ -44,6 +44,10 @@ void MallocTracer::target_did_malloc(Badge<SoftCPU>, FlatPtr address, size_t siz
     ASSERT(region);
     ASSERT(region->is_mmap());
     auto& mmap_region = static_cast<MmapRegion&>(*region);
+
+    // Mark the containing mmap region as a malloc block!
+    mmap_region.set_malloc(true);
+
     auto* shadow_bits = mmap_region.shadow_data() + address - mmap_region.base();
     memset(shadow_bits, 0, size);
 
diff --git a/DevTools/UserspaceEmulator/MmapRegion.cpp b/DevTools/UserspaceEmulator/MmapRegion.cpp
index 3abe4092e7..e507461c85 100644
--- a/DevTools/UserspaceEmulator/MmapRegion.cpp
+++ b/DevTools/UserspaceEmulator/MmapRegion.cpp
@@ -65,13 +65,6 @@ MmapRegion::~MmapRegion()
         free(m_data);
 }
 
-bool MmapRegion::is_malloc_block() const
-{
-    // FIXME: This is obviously incomplete!
-    //        We should somehow know which mmap regions are malloc blocks.
-    return !m_file_backed;
-}
-
 ValueWithShadow<u8> MmapRegion::read8(FlatPtr offset)
 {
     if (!is_readable()) {
diff --git a/DevTools/UserspaceEmulator/MmapRegion.h b/DevTools/UserspaceEmulator/MmapRegion.h
index a32c5271d9..8c088f7f8b 100644
--- a/DevTools/UserspaceEmulator/MmapRegion.h
+++ b/DevTools/UserspaceEmulator/MmapRegion.h
@@ -52,7 +52,8 @@ public:
     bool is_writable() const { return m_prot & PROT_WRITE; }
     bool is_executable() const { return m_prot & PROT_EXEC; }
 
-    bool is_malloc_block() const;
+    bool is_malloc_block() const { return m_malloc; }
+    void set_malloc(bool b) { m_malloc = b; }
 
 private:
     MmapRegion(u32 base, u32 size, int prot);
@@ -62,6 +63,7 @@ private:
     u8* m_shadow_data { nullptr };
     int m_prot { 0 };
     bool m_file_backed { false };
+    bool m_malloc { false };
 };
 
 }