diff --git a/tools/h5PartDcToVtk.cc b/tools/h5PartDcToVtk.cc
index 04bfd68..1884c75 100755
--- a/tools/h5PartDcToVtk.cc
+++ b/tools/h5PartDcToVtk.cc
@@ -167,7 +167,7 @@ int get_option(int argc, const char **argv, const char *opts, const struct long_
     }
   else
     {
-      register char *cp;    /* pointer into current token */
+      register const char *cp;    /* pointer into current token */
 
       /* short command line option */
       opt_opt = argv[opt_ind][sp];
diff --git a/tools/h5PartSurfaceToVtk.cc b/tools/h5PartSurfaceToVtk.cc
index b2eadc3..188bb53 100644
--- a/tools/h5PartSurfaceToVtk.cc
+++ b/tools/h5PartSurfaceToVtk.cc
@@ -176,7 +176,7 @@ int get_option(int argc, const char **argv, const char *opts, const struct long_
     }
   else
     {
-      register char *cp;    /* pointer into current token */
+      register const char *cp;    /* pointer into current token */
 
       /* short command line option */
       opt_opt = argv[opt_ind][sp];