diff --git a/lib/libtuxtxt/teletext.h b/lib/libtuxtxt/teletext.h
index 6bc317171..a7191297d 100644
--- a/lib/libtuxtxt/teletext.h
+++ b/lib/libtuxtxt/teletext.h
@@ -9,6 +9,6 @@ extern int tuxtx_main(int _rc, int pid, int page = 0);
 void tuxtx_stop_subtitle();
 int tuxtx_subtitle_running(int *pid, int *page, int *running);
 void tuxtx_pause_subtitle(bool pause = 1);
-void tuxtx_set_pid(int pid, int page, char * cc);
+void tuxtx_set_pid(int pid, int page, const char * cc);
 
 #endif
diff --git a/lib/libtuxtxt/tuxtxt.cpp b/lib/libtuxtxt/tuxtxt.cpp
index dff5288b1..59e85c922 100644
--- a/lib/libtuxtxt/tuxtxt.cpp
+++ b/lib/libtuxtxt/tuxtxt.cpp
@@ -1538,7 +1538,7 @@ void tuxtx_stop_subtitle()
 	ttx_paused = 0;
 }
 
-void tuxtx_set_pid(int pid, int page, char * cc)
+void tuxtx_set_pid(int pid, int page, const char * cc)
 {
 	if(reader_running)
 		tuxtx_stop_subtitle();
@@ -2471,7 +2471,7 @@ skip_pid:
 /******************************************************************************
  * GetNationalSubset                                                          *
  ******************************************************************************/
-int GetNationalSubset(char *cc)
+int GetNationalSubset(const char *cc)
 {
         if (memcmp(cc, "cze", 3) == 0 || memcmp(cc, "ces", 3) == 0 ||
             memcmp(cc, "slo", 3) == 0 || memcmp(cc, "slk", 3) == 0)
diff --git a/lib/libtuxtxt/tuxtxt.h b/lib/libtuxtxt/tuxtxt.h
index acc43e402..5334f1680 100644
--- a/lib/libtuxtxt/tuxtxt.h
+++ b/lib/libtuxtxt/tuxtxt.h
@@ -1727,7 +1727,7 @@ void RenderPage();
 void DecodePage();
 void UpdateLCD();
 int  Init();
-int  GetNationalSubset(char *country_code);
+int  GetNationalSubset(const char *country_code);
 int  GetTeletextPIDs();
 int  GetRCCode();
 int  eval_triplet(int iOData, tstCachedPage *pstCachedPage,