diff --git a/src/lalr/GrammarCompiler.cpp b/src/lalr/GrammarCompiler.cpp
index cf0a33d..29b0065 100644
--- a/src/lalr/GrammarCompiler.cpp
+++ b/src/lalr/GrammarCompiler.cpp
@@ -41,6 +41,7 @@ GrammarCompiler::GrammarCompiler()
 , lexer_()
 , whitespace_lexer_()
 , parser_state_machine_()
+, labels_enabled_{ false }
 {
     lexer_.reset( new RegexCompiler );
     whitespace_lexer_.reset( new RegexCompiler );
@@ -67,6 +68,11 @@ const ParserStateMachine* GrammarCompiler::parser_state_machine() const
     return parser_state_machine_.get();
 }
 
+void GrammarCompiler::labels_enabled( bool enabled )
+{
+    labels_enabled_ = enabled;
+}
+
 int GrammarCompiler::compile( const char* begin, const char* end, ErrorPolicy* error_policy )
 {
     Grammar grammar;
@@ -239,7 +245,7 @@ void GrammarCompiler::populate_parser_state_machine( const Grammar& grammar, con
         state->index = state_index;
         state->length = grammar_state->count_valid_transitions();
         state->transitions = &transitions[transition_index];
-        state->label = add_string( generator.label_state(*grammar_state) );
+        state->label = labels_enabled_ ? add_string( generator.label_state(*grammar_state) ) : nullptr;
         if ( grammar_state == generator.start_state() )
         {
             start_state = state;
diff --git a/src/lalr/GrammarCompiler.hpp b/src/lalr/GrammarCompiler.hpp
index 8ce1f8b..f3571ac 100644
--- a/src/lalr/GrammarCompiler.hpp
+++ b/src/lalr/GrammarCompiler.hpp
@@ -30,6 +30,7 @@ class GrammarCompiler
     std::unique_ptr<RegexCompiler> lexer_; ///< Allocated lexer state machine.
     std::unique_ptr<RegexCompiler> whitespace_lexer_; ///< Allocated whitespace lexer state machine.
     std::unique_ptr<ParserStateMachine> parser_state_machine_; ///< Allocated parser state machine.
+    bool labels_enabled_; ///< True to generate labels for states and symbols.
 
 public:
     GrammarCompiler();
@@ -37,6 +38,7 @@ public:
     const RegexCompiler* lexer() const;
     const RegexCompiler* whitespace_lexer() const;
     const ParserStateMachine* parser_state_machine() const;
+    void labels_enabled( bool enabled );
     int compile( const char* begin, const char* end, ErrorPolicy* error_policy = nullptr );
 
 private:
diff --git a/src/lalr/lalrc/lalrc.cpp b/src/lalr/lalrc/lalrc.cpp
index 1a2685e..8d8e5b3 100644
--- a/src/lalr/lalrc/lalrc.cpp
+++ b/src/lalr/lalrc/lalrc.cpp
@@ -135,7 +135,14 @@ int main( int argc, char** argv )
             return EXIT_FAILURE;
         }
 
+        // Enable state labels only when generating Graphviz DOT graphs
+        // because generating so many strings takes lots of time and memory.
         GrammarCompiler compiler;
+        if ( dot )
+        {
+            compiler.labels_enabled( true );
+        }
+
         ErrorPolicy error_policy;
         int errors = compiler.compile( &grammar_source[0], &grammar_source[0] + grammar_source.size(), &error_policy );
         if ( errors != 0 )
@@ -344,7 +351,7 @@ void generate_cxx_parser_state_machine( const ParserStateMachine* state_machine
             state->index,
             state->length,
             state->transitions->index,
-            sanitize( state->label ).c_str()
+            state->label ? sanitize( state->label ).c_str() : nullptr
         );
     }
     write( "    {-1, 0, nullptr}\n" );