diff --git a/src/read_graphviz_new.cpp b/src/read_graphviz_new.cpp
index d97292b4..99fc81bc 100644
--- a/src/read_graphviz_new.cpp
+++ b/src/read_graphviz_new.cpp
@@ -53,6 +53,7 @@ namespace boost
 
 namespace read_graphviz_detail
 {
+    static const long max_subgraph_nesting_level = 255;
     struct token
     {
         enum token_type
@@ -527,6 +528,7 @@ namespace read_graphviz_detail
         std::map< subgraph_name, subgraph_info > subgraphs;
         std::string current_subgraph_name;
         int sgcounter; // Counter for anonymous subgraphs
+        long sgnesting_level;
         std::set< std::pair< node_name, node_name > >
             existing_edges; // Used for checking in strict graphs
 
@@ -538,7 +540,7 @@ namespace read_graphviz_detail
         subgraph_member_list& current_members() { return current().members; }
 
         parser(const std::string& gr, parser_result& result)
-        : the_tokenizer(gr), lookahead(), r(result), sgcounter(0)
+        : the_tokenizer(gr), lookahead(), r(result), sgcounter(0), sgnesting_level(0)
         {
             current_subgraph_name = "___root___";
             current() = subgraph_info(); // Initialize root graph
@@ -803,6 +805,10 @@ namespace read_graphviz_detail
                 return name;
             }
             subgraph_name old_sg = current_subgraph_name;
+            if (++sgnesting_level > max_subgraph_nesting_level)
+            {
+                error("Exceeded maximum subgraph nesting level");
+            }
             current_subgraph_name = name;
             if (first_token.type != token::left_brace)
             {
@@ -817,6 +823,7 @@ namespace read_graphviz_detail
             else
                 error("Wanted right brace to end subgraph");
             current_subgraph_name = old_sg;
+            sgnesting_level -= 1;
             return name;
         }