diff --git a/src/hb-buffer.hh b/src/hb-buffer.hh
index bde28933e..a2ad9945c 100644
--- a/src/hb-buffer.hh
+++ b/src/hb-buffer.hh
@@ -450,11 +450,10 @@ struct hb_buffer_t
       }
   }
 
-  void unsafe_to_break_all () { unsafe_to_break_impl (0, len); }
-  void safe_to_break_all ()
+  void clear_glyph_flags (hb_mask_t mask = 0)
   {
     for (unsigned int i = 0; i < len; i++)
-      info[i].mask &= ~HB_GLYPH_FLAG_UNSAFE_TO_BREAK;
+      info[i].mask = (info[i].mask & ~HB_GLYPH_FLAG_DEFINED) | (mask & HB_GLYPH_FLAG_DEFINED);
   }
 };
 DECLARE_NULL_INSTANCE (hb_buffer_t);
diff --git a/src/hb-coretext.cc b/src/hb-coretext.cc
index 4b6c67c1e..a512f3b8b 100644
--- a/src/hb-coretext.cc
+++ b/src/hb-coretext.cc
@@ -1213,7 +1213,7 @@ resize_and_retry:
     }
   }
 
-  buffer->unsafe_to_break_all ();
+  buffer->clear_glyph_flags (HB_GLYPH_FLAG_UNSAFE_TO_BREAK);
 
 #undef FAIL
 
diff --git a/src/hb-directwrite.cc b/src/hb-directwrite.cc
index 2b327e081..dea87b8cd 100644
--- a/src/hb-directwrite.cc
+++ b/src/hb-directwrite.cc
@@ -762,7 +762,7 @@ retry_getglyphs:
 
   if (isRightToLeft) hb_buffer_reverse (buffer);
 
-  buffer->unsafe_to_break_all ();
+  buffer->clear_glyph_flags (HB_GLYPH_FLAG_UNSAFE_TO_BREAK);
 
   delete [] clusterMap;
   delete [] glyphIndices;
diff --git a/src/hb-fallback-shape.cc b/src/hb-fallback-shape.cc
index c5b7c2c23..f8524ecc8 100644
--- a/src/hb-fallback-shape.cc
+++ b/src/hb-fallback-shape.cc
@@ -117,7 +117,7 @@ _hb_fallback_shape (hb_shape_plan_t    *shape_plan HB_UNUSED,
   if (HB_DIRECTION_IS_BACKWARD (direction))
     hb_buffer_reverse (buffer);
 
-  buffer->safe_to_break_all ();
+  buffer->clear_glyph_flags ();
 
   return true;
 }
diff --git a/src/hb-graphite2.cc b/src/hb-graphite2.cc
index 209207f1e..42420ac0b 100644
--- a/src/hb-graphite2.cc
+++ b/src/hb-graphite2.cc
@@ -439,7 +439,7 @@ _hb_graphite2_shape (hb_shape_plan_t    *shape_plan HB_UNUSED,
   if (feats) gr_featureval_destroy (feats);
   gr_seg_destroy (seg);
 
-  buffer->unsafe_to_break_all ();
+  buffer->clear_glyph_flags (HB_GLYPH_FLAG_UNSAFE_TO_BREAK);
 
   return true;
 }
diff --git a/src/hb-ot-layout-gsub-table.hh b/src/hb-ot-layout-gsub-table.hh
index 710c5fbbb..b7ce30135 100644
--- a/src/hb-ot-layout-gsub-table.hh
+++ b/src/hb-ot-layout-gsub-table.hh
@@ -566,7 +566,7 @@ struct AlternateSet
     {
       /* Maybe we can do better than unsafe-to-break all; but since we are
        * changing random state, it would be hard to track that.  Good 'nough. */
-      c->buffer->unsafe_to_break_all ();
+      c->buffer->unsafe_to_break (0, c->buffer->len);
       alt_index = c->random_number () % count + 1;
     }
 
diff --git a/src/hb-uniscribe.cc b/src/hb-uniscribe.cc
index 3dc4c0937..0e5a114f7 100644
--- a/src/hb-uniscribe.cc
+++ b/src/hb-uniscribe.cc
@@ -878,7 +878,7 @@ retry:
   if (backward)
     hb_buffer_reverse (buffer);
 
-  buffer->unsafe_to_break_all ();
+  buffer->clear_glyph_flags (HB_GLYPH_FLAG_UNSAFE_TO_BREAK);
 
   /* Wow, done! */
   return true;