diff --git a/bbs/subedit.cpp b/bbs/subedit.cpp
index d4ac5f457..145e20fd8 100644
--- a/bbs/subedit.cpp
+++ b/bbs/subedit.cpp
@@ -333,8 +333,9 @@ static void modify_sub(int n) {
         if (a()->subs().sub(n).name == "** New WWIV Message Sub **") {
           a()->subs().sub(n).name = a()->subs().sub(n).desc;
         }
-        if (a()->subs().sub(n).filename == "NONAME") {
-          a()->subs().sub(n).filename = a()->subs().sub(n).nets[0].stype;
+        const auto stype = a()->subs().sub(n).nets[0].stype;
+        if (a()->subs().sub(n).filename == "NONAME" && stype.size() <= 8) {
+          a()->subs().sub(n).filename = stype;
         }
       } else if (ch2 == 'D' || ch2 == 'M') {
         bout.nl();
diff --git a/sdk/subxtr.cpp b/sdk/subxtr.cpp
index 89c2ba302..bdca5fedc 100644
--- a/sdk/subxtr.cpp
+++ b/sdk/subxtr.cpp
@@ -325,11 +325,18 @@ bool Subs::Save() {
   std::vector<xtrasubsrec> xsubs;
 
   for (const auto& s : subs_) {
-    subboardrec_422_t ls = {};
-    xtrasubsrec lx = {};
-    to_char_array(ls.name, s.name);
-    to_char_array(lx.desc, s.desc);
-    to_char_array(ls.filename, s.filename);
+    // Only copy over what data fits in the old format.
+    subboardrec_422_t ls{};
+    xtrasubsrec lx{};
+    if (s.name.size() < sizeof ls.name) {
+      to_char_array(ls.name, s.name);
+    }
+    if (s.desc.size() < sizeof lx.desc) {
+      to_char_array(lx.desc, s.desc);
+    }
+    if (s.filename.size() < sizeof ls.filename) {
+      to_char_array(ls.filename, s.filename);
+    }
     ls.key = s.key;
     ls.readsl = s.readsl;
     ls.postsl = s.postsl;