diff --git a/programs/ssl/ssl_server.c b/programs/ssl/ssl_server.c
index 67fbd2e..e0af1b0 100644
--- a/programs/ssl/ssl_server.c
+++ b/programs/ssl/ssl_server.c
@@ -80,7 +80,7 @@
 
 #define DEBUG_LEVEL 0
 
-void my_debug( void *ctx, int level, char *str )
+void my_debug( void *ctx, int level, const char *str )
 {
     if( level < DEBUG_LEVEL )
     {