diff --git a/src/graph/graph.hh b/src/graph/graph.hh
index 294a99991..73f897d2f 100644
--- a/src/graph/graph.hh
+++ b/src/graph/graph.hh
@@ -401,9 +401,10 @@ struct graph_t
     return vertices_[i].obj;
   }
 
-  void add_buffer (char* buffer)
+  bool add_buffer (char* buffer)
   {
     buffers.push (buffer);
+    return !buffers.in_error ();
   }
 
   /*
diff --git a/src/graph/gsubgpos-context.cc b/src/graph/gsubgpos-context.cc
index b2044426d..d66eb49cf 100644
--- a/src/graph/gsubgpos-context.cc
+++ b/src/graph/gsubgpos-context.cc
@@ -52,7 +52,11 @@ unsigned gsubgpos_graph_context_t::create_node (unsigned size)
   if (!buffer)
     return -1;
 
-  add_buffer (buffer);
+  if (!add_buffer (buffer)) {
+    // Allocation did not get stored for freeing later.
+    hb_free (buffer);
+    return -1;
+  }
 
   return graph.new_node (buffer, buffer + size);
 }
diff --git a/src/graph/gsubgpos-context.hh b/src/graph/gsubgpos-context.hh
index 9fe9662e6..26b7cfe4d 100644
--- a/src/graph/gsubgpos-context.hh
+++ b/src/graph/gsubgpos-context.hh
@@ -47,9 +47,9 @@ struct gsubgpos_graph_context_t
 
   HB_INTERNAL unsigned create_node (unsigned size);
 
-  void add_buffer (char* buffer)
+  bool add_buffer (char* buffer)
   {
-    graph.add_buffer (buffer);
+    return graph.add_buffer (buffer);
   }
 
  private:
diff --git a/test/fuzzing/graphs/clusterfuzz-testcase-minimized-hb-repacker-fuzzer-6419865171525632 b/test/fuzzing/graphs/clusterfuzz-testcase-minimized-hb-repacker-fuzzer-6419865171525632
new file mode 100644
index 000000000..2deb99fe6
Binary files /dev/null and b/test/fuzzing/graphs/clusterfuzz-testcase-minimized-hb-repacker-fuzzer-6419865171525632 differ