diff --git a/xsltproc/xsltproc.c b/xsltproc/xsltproc.c
index 3f49cec3..ead38930 100644
--- a/xsltproc/xsltproc.c
+++ b/xsltproc/xsltproc.c
@@ -287,7 +287,7 @@ static void startTimer(void)
 {
     begin=clock();
 }
-static void endTimer(char *format, ...)
+static void endTimer(const char *format, ...)
 {
     long msec;
     va_list ap;
@@ -313,7 +313,7 @@ static void startTimer(void)
    * Do nothing
    */
 }
-static void endTimer(char *format, ...)
+static void endTimer(const char *format, ...)
 {
   /*
    * We cannot do anything because we don't have a timing function