diff --git a/lib/memdebug.c b/lib/memdebug.c
index 4ccdc727d29da3c109131ee8820fe2a9aca84a8a..f0e104a6dcee2c8db9a6f8d5a6aa3084fdee56a0 100644
--- a/lib/memdebug.c
+++ b/lib/memdebug.c
@@ -58,7 +58,7 @@
 FILE *logfile;
 
 /* this sets the log file name */
-void curl_memdebug(char *logname)
+void curl_memdebug(const char *logname)
 {
   logfile = fopen(logname, "w");
 }
diff --git a/lib/memdebug.h b/lib/memdebug.h
index 419b8b943acb914037889d546dbb57362f589b36..2a6a35ac2e7f9f3965010b6dcdc4913a3620881b 100644
--- a/lib/memdebug.h
+++ b/lib/memdebug.h
@@ -11,7 +11,7 @@ void *curl_domalloc(size_t size, int line, const char *source);
 void *curl_dorealloc(void *ptr, size_t size, int line, const char *source);
 void curl_dofree(void *ptr, int line, const char *source);
 char *curl_dostrdup(const char *str, int line, const char *source);
-void curl_memdebug(char *logname);
+void curl_memdebug(const char *logname);
 
 /* file descriptor manipulators */
 int curl_socket(int domain, int type, int protocol, int, const char *);