diff --git a/environment.cpp b/environment.cpp
index 77f7622..839553e 100644
--- a/environment.cpp
+++ b/environment.cpp
@@ -175,7 +175,7 @@ namespace {
 		return i;
 	}
 
-	void Environment::echo(const char *fmt, ...) {
+	void Environment::echo(const char *fmt, ...) const {
 		if (_echo && !_startup) {
 			for (unsigned i = 0; i < _indent; ++i) {
 				fputc(' ', stderr);
diff --git a/environment.h b/environment.h
index 23df1e3..4829d14 100644
--- a/environment.h
+++ b/environment.h
@@ -100,7 +100,7 @@ public:
 	const_iterator find( const std::string & key ) const;
 
 
-	void echo(const char *format, ...);
+	void echo(const char *format, ...) const;
 
 	template<class FX>
 	void indent_and(FX &&fx) {