diff --git a/include/osmocom/core/logging.h b/include/osmocom/core/logging.h
index bbaef45..989228b 100644
--- a/include/osmocom/core/logging.h
+++ b/include/osmocom/core/logging.h
@@ -28,7 +28,7 @@
 #endif
 
 
-void osmo_vlogp(int subsys, int level, char *file, int line,
+void osmo_vlogp(int subsys, int level, const char *file, int line,
 		int cont, const char *format, va_list ap);
 
 void logp(int subsys, const char *file, int line, int cont, const char *format, ...) __attribute__ ((format (printf, 5, 6)));