diff --git a/honoka/plugins/romkan.cpp b/honoka/plugins/romkan.cpp
index fd1dc8c..fed1010 100644
--- a/honoka/plugins/romkan.cpp
+++ b/honoka/plugins/romkan.cpp
@@ -524,6 +524,7 @@
         }
     }
 
+    if (!hookp.length())  return false;
     if ((buf.length() < hookp.length()) || (!hookp.length())) return false;
     else if (buf.substr(0,hookp.length()) == hookp) {
         return inputEvent(key);
@@ -606,6 +607,7 @@
         if ((key.code == SCIM_KEY_Return) ||
             (key.code == SCIM_KEY_Linefeed) ||
             (key.code == SCIM_KEY_Tab)) return false;
+        if (!isprint(key.get_ascii_code())) return false;
         insert(key.get_ascii_code());
         return true;
     }