diff --git a/libsolidity/SourceReferenceFormatter.cpp b/libsolidity/SourceReferenceFormatter.cpp
index 1a7d12a95..c61f9b685 100644
--- a/libsolidity/SourceReferenceFormatter.cpp
+++ b/libsolidity/SourceReferenceFormatter.cpp
@@ -61,7 +61,7 @@ void SourceReferenceFormatter::printSourceLocation(ostream& _stream,
 void SourceReferenceFormatter::printExceptionInformation(ostream& _stream,
 														 Exception const& _exception,
 														 string const& _name,
-														 CompilerStack& _compiler)
+														 CompilerStack const& _compiler)
 {
 	Location const* location = boost::get_error_info<errinfo_sourceLocation>(_exception);
 	Scanner const* scanner;
diff --git a/libsolidity/SourceReferenceFormatter.h b/libsolidity/SourceReferenceFormatter.h
index 9b5567045..8e3f126f0 100644
--- a/libsolidity/SourceReferenceFormatter.h
+++ b/libsolidity/SourceReferenceFormatter.h
@@ -41,7 +41,7 @@ struct SourceReferenceFormatter
 public:
 	static void printSourceLocation(std::ostream& _stream, Location const& _location, Scanner const& _scanner);
 	static void printExceptionInformation(std::ostream& _stream, Exception const& _exception,
-										  std::string const& _name, CompilerStack& _compiler);
+										  std::string const& _name, CompilerStack const& _compiler);
 };
 
 }