diff --git a/log_manager/log_manager.cc b/log_manager/log_manager.cc
index c8f96266e..4138fdcb3 100644
--- a/log_manager/log_manager.cc
+++ b/log_manager/log_manager.cc
@@ -249,7 +249,7 @@ static int  logmanager_write_log(
         bool         use_valist,
         bool         spread_down,
         size_t       len,
-        char*        str,
+        const char*  str,
         va_list      valist);
 
 static blockbuf_t* blockbuf_init(logfile_id_t id);
@@ -603,7 +603,7 @@ static int logmanager_write_log(
         bool          use_valist,
         bool          spread_down,
         size_t        str_len,
-        char*         str,
+        const char*   str,
         va_list       valist)
 {
         logfile_t*   lf;
@@ -617,7 +617,7 @@ static int logmanager_write_log(
         CHK_LOGMANAGER(lm);
         
         if (id < LOGFILE_FIRST || id > LOGFILE_LAST) {
-                char* errstr = "Invalid logfile id argument.";
+                const char* errstr = "Invalid logfile id argument.";
                 /**
                  * invalid id, since we don't have logfile yet.
                  */
@@ -1092,7 +1092,7 @@ static bool logfile_set_enabled(
         CHK_LOGMANAGER(lm);
         
         if (id < LOGFILE_FIRST || id > LOGFILE_LAST) {
-            char* errstr = "Invalid logfile id argument.";
+            const char* errstr = "Invalid logfile id argument.";
             /**
              * invalid id, since we don't have logfile yet.
              */
@@ -1146,7 +1146,7 @@ return_succp:
 
 int skygw_log_write_flush(
         logfile_id_t  id,
-        char*         str,
+        const char*   str,
         ...)
 {
         int     err = 0;
@@ -1199,7 +1199,7 @@ return_err:
 
 int skygw_log_write(
         logfile_id_t  id,
-        char*         str,
+        const char*   str,
         ...)
 {
         int     err = 0;
diff --git a/log_manager/log_manager.h b/log_manager/log_manager.h
index b96669fa2..b3dc73f18 100644
--- a/log_manager/log_manager.h
+++ b/log_manager/log_manager.h
@@ -66,9 +66,9 @@ void skygw_logmanager_exit(void);
  * free private write buffer list
  */
 void skygw_log_done(void);
-int  skygw_log_write(logfile_id_t id, char* format, ...);
+int  skygw_log_write(logfile_id_t id, const char* format, ...);
 int  skygw_log_flush(logfile_id_t id);
-int  skygw_log_write_flush(logfile_id_t id, char* format, ...);
+int  skygw_log_write_flush(logfile_id_t id, const char* format, ...);
 int  skygw_log_enable(logfile_id_t id);
 int  skygw_log_disable(logfile_id_t id);
 
diff --git a/server/core/dcb.c b/server/core/dcb.c
index 969702cf4..58d759332 100644
--- a/server/core/dcb.c
+++ b/server/core/dcb.c
@@ -1772,7 +1772,7 @@ int		rval = 1;
  * @return		Non-zero (true) if the callback was removed
  */
 int
-dcb_remove_callback(DCB *dcb, DCB_REASON reason, int (*callback)(struct dcb *, DCB_REASON), void *userdata)
+dcb_remove_callback(DCB *dcb, DCB_REASON reason, int (*callback)(struct dcb *, DCB_REASON, void *), void *userdata)
 {
 DCB_CALLBACK	*cb, *pcb = NULL;
 int		rval = 0;
diff --git a/server/include/dcb.h b/server/include/dcb.h
index 88964fc31..956bb3ef6 100644
--- a/server/include/dcb.h
+++ b/server/include/dcb.h
@@ -289,7 +289,7 @@ void		dcb_hashtable_stats(DCB *, void *);	/**< Print statisitics */
 void            dcb_add_to_zombieslist(DCB* dcb);
 int		dcb_add_callback(DCB *, DCB_REASON, int	(*)(struct dcb *, DCB_REASON, void *),
 			 void *);
-int		dcb_remove_callback(DCB *, DCB_REASON, int	(*)(struct dcb *, DCB_REASON),
+int		dcb_remove_callback(DCB *, DCB_REASON, int	(*)(struct dcb *, DCB_REASON, void *),
 			 void *);
 int		dcb_isvalid(DCB *);			/* Check the DCB is in the linked list */