diff --git a/lib/include/srsran/phy/io/filesource.h b/lib/include/srsran/phy/io/filesource.h
index c33e6564e..f264a6a4a 100644
--- a/lib/include/srsran/phy/io/filesource.h
+++ b/lib/include/srsran/phy/io/filesource.h
@@ -35,7 +35,7 @@ typedef struct SRSRAN_API {
   srsran_datatype_t type;
 } srsran_filesource_t;
 
-SRSRAN_API int srsran_filesource_init(srsran_filesource_t* q, char* filename, srsran_datatype_t type);
+SRSRAN_API int srsran_filesource_init(srsran_filesource_t* q, const char* filename, srsran_datatype_t type);
 
 SRSRAN_API void srsran_filesource_free(srsran_filesource_t* q);
 
diff --git a/lib/src/phy/io/filesource.c b/lib/src/phy/io/filesource.c
index 39cdfb59a..0f709157d 100644
--- a/lib/src/phy/io/filesource.c
+++ b/lib/src/phy/io/filesource.c
@@ -17,7 +17,7 @@
 #include "srsran/phy/io/filesource.h"
 #include "srsran/phy/utils/debug.h"
 
-int srsran_filesource_init(srsran_filesource_t* q, char* filename, srsran_datatype_t type)
+int srsran_filesource_init(srsran_filesource_t* q, const char* filename, srsran_datatype_t type)
 {
   bzero(q, sizeof(srsran_filesource_t));
   q->f = fopen(filename, "r");