diff --git a/src/osdep/osdep.c b/src/osdep/osdep.c
index f16625f93..56b4323b3 100644
--- a/src/osdep/osdep.c
+++ b/src/osdep/osdep.c
@@ -1023,7 +1023,7 @@ set_highpri(void)
 #endif
 
 
-char *
+const char *
 get_system_str(int xwin)
 {
 	return xwin ? SYSTEM_STR "-xwin" : SYSTEM_STR;
diff --git a/src/osdep/osdep.h b/src/osdep/osdep.h
index e4d1883b9..3e2e667d7 100644
--- a/src/osdep/osdep.h
+++ b/src/osdep/osdep.h
@@ -61,7 +61,7 @@ void prealloc_truncate(int, off_t);
 static inline void prealloc_truncate(int x, int y) { }
 #endif
 
-char *get_system_str(int);
+const char *get_system_str(int);
 
 int set_nonblocking_fd(int);
 int set_blocking_fd(int);