diff --git a/src/lang/italian.txt b/src/lang/italian.txt
index 5e59426565..90ace0f0f1 100644
--- a/src/lang/italian.txt
+++ b/src/lang/italian.txt
@@ -1,6 +1,6 @@
 ##name Italian
 ##ownname Italiano
-##isocode it
+##isocode it_IT
 ##plural 0
 ##case ms mp fs fp
 ##gender m f
diff --git a/src/lang/unfinished/frisian.txt b/src/lang/unfinished/frisian.txt
index e3dc1b86a1..72f32c0855 100644
--- a/src/lang/unfinished/frisian.txt
+++ b/src/lang/unfinished/frisian.txt
@@ -1,6 +1,6 @@
 ##name Frisian
 ##ownname Frysk
-##isocode fy
+##isocode fy_NL
 
 ##id 0x0000
 STR_NULL                                                        :
diff --git a/src/newgrf_text.cpp b/src/newgrf_text.cpp
index 74090d0678..f9ef1ec5c3 100644
--- a/src/newgrf_text.cpp
+++ b/src/newgrf_text.cpp
@@ -101,7 +101,7 @@ const iso_grf iso_codes[] = {
 	{"es_ES", GRFLX_SPANISH},
 	{"af_ZA", GRFLX_AFRIKAANS},
 	{"hr_HR", GRFLX_CROATIAN},
-	{"cs_CS", GRFLX_CZECH},
+	{"cs_CZ", GRFLX_CZECH},
 	{"ca_ES", GRFLX_CATALAN},
 	{"da_DA", GRFLX_DANISH},
 	{"nl_NL", GRFLX_DUTCH},