diff --git a/src/hb-buffer-private.hh b/src/hb-buffer-private.hh
index f544c8244..d83d1300b 100644
--- a/src/hb-buffer-private.hh
+++ b/src/hb-buffer-private.hh
@@ -66,13 +66,15 @@ struct _hb_buffer_t {
   unsigned int len; /* Length of ->info and ->pos arrays */
   unsigned int out_len; /* Length of ->out array if have_output */
 
-  unsigned int serial;
-
   unsigned int allocated; /* Length of allocated arrays */
   hb_glyph_info_t     *info;
   hb_glyph_info_t     *out_info;
   hb_glyph_position_t *pos;
 
+  unsigned int serial;
+  uint8_t allocated_var_bytes[8];
+  const char *allocated_var_owner[8];
+
 
   /* Methods */
 
@@ -82,6 +84,25 @@ struct _hb_buffer_t {
   { return have_output? out_len : idx; }
   inline unsigned int next_serial (void) { return serial++; }
 
+
+  HB_INTERNAL void allocate_var (unsigned int byte_i, unsigned int count, const char *owner);
+  HB_INTERNAL void deallocate_var (unsigned int byte_i, unsigned int count, const char *owner);
+
+  inline void allocate_var_8 (unsigned int var_num, unsigned int i, const char *owner)
+  { assert (var_num < 2 && i < 4); allocate_var (var_num * 4 + i, 1, owner); }
+  inline void allocate_var_16 (unsigned int var_num, unsigned int i, const char *owner)
+  { assert (var_num < 2 && i < 2); allocate_var (var_num * 4 + i * 2, 2, owner); }
+  inline void allocate_var_32 (unsigned int var_num, const char *owner)
+  { assert (var_num < 2); allocate_var (var_num * 4, 4, owner); }
+
+  inline void deallocate_var_8 (unsigned int var_num, unsigned int i, const char *owner)
+  { assert (var_num < 2 && i < 4); deallocate_var (var_num * 4 + i, 1, owner); }
+  inline void deallocate_var_16 (unsigned int var_num, unsigned int i, const char *owner)
+  { assert (var_num < 2 && i < 2); deallocate_var (var_num * 4 + i * 2, 2, owner); }
+  inline void deallocate_var_32 (unsigned int var_num, const char *owner)
+  { assert (var_num < 2); deallocate_var (var_num * 4, 4, owner); }
+
+
   HB_INTERNAL void add (hb_codepoint_t  codepoint,
 			hb_mask_t       mask,
 			unsigned int    cluster);
diff --git a/src/hb-buffer.cc b/src/hb-buffer.cc
index 716f858b2..2b5760d31 100644
--- a/src/hb-buffer.cc
+++ b/src/hb-buffer.cc
@@ -153,6 +153,8 @@ hb_buffer_t::reset (void)
   out_len = 0;
 
   serial = 0;
+  memset (allocated_var_bytes, 0, sizeof allocated_var_bytes);
+  memset (allocated_var_owner, 0, sizeof allocated_var_owner);
 
   out_info = info;
 }
@@ -387,6 +389,26 @@ hb_buffer_t::reverse_clusters (void)
 }
 
 
+void hb_buffer_t::allocate_var (unsigned int byte_i, unsigned int count, const char *owner)
+{
+  assert (byte_i < 8 && byte_i + count < 8);
+  for (unsigned int i = byte_i; i < byte_i + count; i++) {
+    assert (!allocated_var_bytes[i]);
+    allocated_var_bytes[i]++;
+    allocated_var_owner[i] = owner;
+  }
+}
+
+void hb_buffer_t::deallocate_var (unsigned int byte_i, unsigned int count, const char *owner)
+{
+  assert (byte_i < 8 && byte_i + count < 8);
+  for (unsigned int i = byte_i; i < byte_i + count; i++) {
+    assert (allocated_var_bytes[i] && allocated_var_owner[i] == owner);
+    allocated_var_bytes[i]--;
+  }
+}
+
+
 /* Public API */
 
 hb_buffer_t *