diff --git a/AK/String.h b/AK/String.h
index 061d697b09..52c006e0be 100644
--- a/AK/String.h
+++ b/AK/String.h
@@ -142,6 +142,7 @@ public:
     bool is_null() const { return !m_impl; }
     ALWAYS_INLINE bool is_empty() const { return length() == 0; }
     ALWAYS_INLINE size_t length() const { return m_impl ? m_impl->length() : 0; }
+    // Includes NUL-terminator, if non-nullptr.
     ALWAYS_INLINE const char* characters() const { return m_impl ? m_impl->characters() : nullptr; }
 
     ALWAYS_INLINE ReadonlyBytes bytes() const { return m_impl ? m_impl->bytes() : nullptr; }
diff --git a/AK/StringImpl.h b/AK/StringImpl.h
index 47ae2c6905..e85798a06c 100644
--- a/AK/StringImpl.h
+++ b/AK/StringImpl.h
@@ -59,6 +59,7 @@ public:
     ~StringImpl();
 
     size_t length() const { return m_length; }
+    // Includes NUL-terminator.
     const char* characters() const { return &m_inline_buffer[0]; }
 
     ALWAYS_INLINE ReadonlyBytes bytes() const { return { characters(), length() }; }