diff --git a/programs/ssl/ssl_client1.c b/programs/ssl/ssl_client1.c
index 455f080..4366853 100644
--- a/programs/ssl/ssl_client1.c
+++ b/programs/ssl/ssl_client1.c
@@ -38,7 +38,7 @@
 
 #define DEBUG_LEVEL 4
 
-void my_debug( void *ctx, int level, char *str )
+void my_debug( void *ctx, int level, const char *str )
 {
     if( level < DEBUG_LEVEL )
     {
diff --git a/programs/ssl/ssl_client2.c b/programs/ssl/ssl_client2.c
index 642ef8c..04613e7 100644
--- a/programs/ssl/ssl_client2.c
+++ b/programs/ssl/ssl_client2.c
@@ -53,7 +53,7 @@
     char *request_page;         /* page on server to request            */
 } opt;
 
-void my_debug( void *ctx, int level, char *str )
+void my_debug( void *ctx, int level, const char *str )
 {
     if( level < opt.debug_level )
     {
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 )
     {
diff --git a/programs/test/ssl_test.c b/programs/test/ssl_test.c
index 6ba4069..f12c2e9 100644
--- a/programs/test/ssl_test.c
+++ b/programs/test/ssl_test.c
@@ -113,7 +113,7 @@
     return( u );
 }
 
-void my_debug( void *ctx, int level, char *str )
+void my_debug( void *ctx, int level, const char *str )
 {
     if( level < ((struct options *) ctx)->debug_level )
         fprintf( stderr, "%s", str );