diff --git a/src/hb-cache.hh b/src/hb-cache.hh
index 55a80024f..3bcfc9e3d 100644
--- a/src/hb-cache.hh
+++ b/src/hb-cache.hh
@@ -32,13 +32,18 @@
 
 /* Implements a lockfree cache for int->int functions. */
 
-template <unsigned int key_bits=16, unsigned int value_bits=8 + 32 - key_bits, unsigned int cache_bits=8>
+template <unsigned int key_bits=16,
+	 unsigned int value_bits=8 + 32 - key_bits,
+	 unsigned int cache_bits=8,
+	 bool thread_safe=true>
 struct hb_cache_t
 {
   static_assert ((key_bits >= cache_bits), "");
   static_assert ((key_bits + value_bits - cache_bits <= 8 * sizeof (hb_atomic_int_t)), "");
   static_assert (sizeof (hb_atomic_int_t) == sizeof (unsigned int), "");
 
+  using item_t = typename std::conditional<thread_safe, hb_atomic_int_t, int>::type;
+
   void init () { clear (); }
   void fini () {}
 
@@ -70,11 +75,15 @@ struct hb_cache_t
   }
 
   private:
-  hb_atomic_int_t values[1u<<cache_bits];
+  item_t values[1u<<cache_bits];
 };
 
-typedef hb_cache_t<21, 16, 8> hb_cmap_cache_t;
-typedef hb_cache_t<16, 24, 8> hb_advance_cache_t;
+
+template <bool thread_safe = true>
+using hb_cmap_cache_t = hb_cache_t<21, 16, 8, thread_safe>;
+
+template <bool thread_safe = true>
+using hb_advance_cache_t = hb_cache_t<16, 24, 8, thread_safe>;
 
 
 #endif /* HB_CACHE_HH */
diff --git a/src/hb-ft.cc b/src/hb-ft.cc
index 8965fcb4f..081d716cb 100644
--- a/src/hb-ft.cc
+++ b/src/hb-ft.cc
@@ -89,7 +89,7 @@ struct hb_ft_font_t
   mutable hb_mutex_t lock;
   FT_Face ft_face;
   mutable unsigned cached_serial;
-  mutable hb_advance_cache_t advance_cache;
+  mutable hb_advance_cache_t<false> advance_cache;
 };
 
 static hb_ft_font_t *
diff --git a/src/hb-ot-font.cc b/src/hb-ot-font.cc
index ef28c7d65..78230bd1a 100644
--- a/src/hb-ot-font.cc
+++ b/src/hb-ot-font.cc
@@ -65,7 +65,7 @@ struct hb_ot_font_t
 
   /* h_advance caching */
   mutable hb_atomic_int_t cached_coords_serial;
-  mutable hb_atomic_ptr_t<hb_advance_cache_t> advance_cache;
+  mutable hb_atomic_ptr_t<hb_advance_cache_t<>> advance_cache;
 };
 
 static hb_ot_font_t *
@@ -161,14 +161,14 @@ hb_ot_get_glyph_h_advances (hb_font_t* font, void* font_data,
   bool use_cache = false;
 #endif
 
-  hb_advance_cache_t *cache = nullptr;
+  hb_advance_cache_t<> *cache = nullptr;
   if (use_cache)
   {
   retry:
     cache = ot_font->advance_cache.get_acquire ();
     if (unlikely (!cache))
     {
-      cache = (hb_advance_cache_t *) hb_malloc (sizeof (hb_advance_cache_t));
+      cache = (hb_advance_cache_t<> *) hb_malloc (sizeof (hb_advance_cache_t<>));
       if (unlikely (!cache))
       {
 	use_cache = false;