diff --git a/src/core/charset/charset.c b/src/core/charset/charset.c
index 9e68cd8..8482a5f 100644
--- a/src/core/charset/charset.c
+++ b/src/core/charset/charset.c
@@ -219,6 +219,12 @@ LIB3270_EXPORT void lib3270_reset_charset(H3270 *hSession, const char * host, co
 
 	#define replace_pointer(x,v) if(x) { lib3270_free(x); }; x = strdup(v)
 
+	if(!host)
+		host = "us";
+
+	if(!display)
+		display = "ISO-8859-1";
+
 	replace_pointer(hSession->charset.host, host);
 	replace_pointer(hSession->charset.display,display);
 
diff --git a/src/include/lib3270-internals.h b/src/include/lib3270-internals.h
index f04a191..7f08a8b 100644
--- a/src/include/lib3270-internals.h
+++ b/src/include/lib3270-internals.h
@@ -274,8 +274,6 @@ struct lib3270_text
 #endif // !LIB3270_TA
 
 #define LIB3270_MB_MAX					16
-#define LIB3270_DEFAULT_CGEN			0x02b90000
-#define LIB3270_DEFAULT_CSET			0x00000025
 
 #define LIB3270_FULL_MODEL_NAME_LENGTH	13
 #define LIB3270_LU_MAX					32
diff --git a/src/include/lib3270/charset.h b/src/include/lib3270/charset.h
index ff19d10..deeebf3 100644
--- a/src/include/lib3270/charset.h
+++ b/src/include/lib3270/charset.h
@@ -37,6 +37,9 @@
 	extern "C" {
 #endif
 
+	#define LIB3270_DEFAULT_CGEN			0x02b90000
+	#define LIB3270_DEFAULT_CSET			0x00000025
+
 	struct lib3270_charset
 	{
 		char			* host;
--
libgit2 0.21.2