diff --git a/ChangeLog b/ChangeLog
index 43eb5e704..4b53b40f2 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,5 +1,8 @@
 2004-10-20  Alexandre Duret-Lutz  <adl@src.lip6.fr>
 
+	* src/misc/modgray.hh (loopless_modular_mixed_radix_gray_code::done,
+	loopless_modular_mixed_radix_gray_code::last): Declare as const.
+
 	* src/misc/bareword.hh, src/misc/bareword.cc: New files.
 	* src/misc/Makefile.am (libmisc_la_SOURCES, misc_HEADERS): Add them.
 
diff --git a/src/misc/modgray.hh b/src/misc/modgray.hh
index 74865f526..0c101f754 100644
--- a/src/misc/modgray.hh
+++ b/src/misc/modgray.hh
@@ -110,14 +110,14 @@ namespace spot
     /// At this point it is still OK to call next(), and then done() will
     /// become true.
     bool
-    last()
+    last() const
     {
       return f_[0] == n_;
     }
 
     /// Whether all tuple have been explored.
     bool
-    done()
+    done() const
     {
       return done_;
     }