diff --git a/src/graph/classdef-graph.hh b/src/graph/classdef-graph.hh
index c2e24a706..4ae0c13ac 100644
--- a/src/graph/classdef-graph.hh
+++ b/src/graph/classdef-graph.hh
@@ -94,7 +94,13 @@ struct ClassDef : public OT::ClassDef
     }
 
     hb_bytes_t class_def_copy = serializer.copy_bytes ();
-    c.add_buffer ((char *) class_def_copy.arrayZ); // Give ownership to the context, it will cleanup the buffer.
+    if (!class_def_copy.arrayZ) return false;
+    // Give ownership to the context, it will cleanup the buffer.
+    if (!c.add_buffer ((char *) class_def_copy.arrayZ))
+    {
+      hb_free ((char *) class_def_copy.arrayZ);
+      return false;
+    }
 
     auto& obj = c.graph.vertices_[dest_obj].obj;
     obj.head = (char *) class_def_copy.arrayZ;
diff --git a/src/graph/coverage-graph.hh b/src/graph/coverage-graph.hh
index 49d093631..bd6e91a1f 100644
--- a/src/graph/coverage-graph.hh
+++ b/src/graph/coverage-graph.hh
@@ -118,7 +118,13 @@ struct Coverage : public OT::Layout::Common::Coverage
     }
 
     hb_bytes_t coverage_copy = serializer.copy_bytes ();
-    c.add_buffer ((char *) coverage_copy.arrayZ); // Give ownership to the context, it will cleanup the buffer.
+    if (!coverage_copy.arrayZ) return false;
+    // Give ownership to the context, it will cleanup the buffer.
+    if (!c.add_buffer ((char *) coverage_copy.arrayZ))
+    {
+      hb_free ((char *) coverage_copy.arrayZ);
+      return false;
+    }
 
     auto& obj = c.graph.vertices_[dest_obj].obj;
     obj.head = (char *) coverage_copy.arrayZ;
diff --git a/src/graph/gsubgpos-graph.hh b/src/graph/gsubgpos-graph.hh
index c17063840..78d509632 100644
--- a/src/graph/gsubgpos-graph.hh
+++ b/src/graph/gsubgpos-graph.hh
@@ -166,7 +166,7 @@ struct Lookup : public OT::Lookup
     }
 
     if (all_new_subtables) {
-      add_sub_tables (c, this_index, type, all_new_subtables);
+      return add_sub_tables (c, this_index, type, all_new_subtables);
     }
 
     return true;
@@ -184,7 +184,7 @@ struct Lookup : public OT::Lookup
     return sub_table->split_subtables (c, parent_idx, objidx);
   }
 
-  void add_sub_tables (gsubgpos_graph_context_t& c,
+  bool add_sub_tables (gsubgpos_graph_context_t& c,
                        unsigned this_index,
                        unsigned type,
                        hb_vector_t<hb_pair_t<unsigned, hb_vector_t<unsigned>>>& subtable_ids)
@@ -200,7 +200,12 @@ struct Lookup : public OT::Lookup
     size_t new_size = v.table_size ()
                       + new_subtable_count * OT::Offset16::static_size;
     char* buffer = (char*) hb_calloc (1, new_size);
-    c.add_buffer (buffer);
+    if (!buffer) return false;
+    if (!c.add_buffer (buffer))
+    {
+      hb_free (buffer);
+     return false;
+    }
     hb_memcpy (buffer, v.obj.head, v.table_size());
 
     v.obj.head = buffer;
@@ -239,6 +244,7 @@ struct Lookup : public OT::Lookup
     // The head location of the lookup has changed, invalidating the lookups map entry
     // in the context. Update the map.
     c.lookups.set (this_index, new_lookup);
+    return true;
   }
 
   void fix_existing_subtable_links (gsubgpos_graph_context_t& c,