--- src/app-utils/gnc-sx-instance-model.c
+++ src/app-utils/gnc-sx-instance-model.c
@@ -262,5 +262,5 @@
 {
     Account *template_root, *sx_template_acct;
-    char sx_guid_str[GUID_ENCODING_LENGTH];
+    char sx_guid_str[GUID_ENCODING_LENGTH+1];
 
     template_root = gnc_book_get_template_root(gnc_get_current_book());
@@ -924,5 +924,5 @@
     if (*split_acct == NULL)
     {
-        char guid_str[GUID_ENCODING_LENGTH];
+        char guid_str[GUID_ENCODING_LENGTH+1];
         GString *err;
         guid_to_string_buff((const GUID*)acct_guid, guid_str);