diff --git a/honoka/libhonoka/preeditor.cpp b/honoka/libhonoka/preeditor.cpp
index bdef56f..beb5380 100644
--- a/honoka/libhonoka/preeditor.cpp
+++ b/honoka/libhonoka/preeditor.cpp
@@ -416,11 +416,16 @@
 
 
 /*!
-    \fn Honoka::PreEditor::isPrintable(KeyEvent &key)
+    \fn Honoka::PreEditor::isPrintable(const KeyEvent &key)
  */
-bool Honoka::PreEditor::isPrintable(KeyEvent &key)
+bool Honoka::PreEditor::isPrintable(const KeyEvent &key)
 {
-    if (key.get_unicode_code()) return true;
+    if ((key.code == SCIM_KEY_Return) ||
+        (key.code == SCIM_KEY_Linefeed) ||
+        (key.code == SCIM_KEY_Tab)) return false;
+
+    if (key.get_unicode_code() && (!key.is_alt_down()) && (!key.is_control_down())) return true;
+    return false;
 }
 
 
diff --git a/honoka/libhonoka/preeditor.h b/honoka/libhonoka/preeditor.h
index 111efd5..0c3447c 100644
--- a/honoka/libhonoka/preeditor.h
+++ b/honoka/libhonoka/preeditor.h
@@ -91,7 +91,7 @@
     virtual void unSelected();
     static const WideString getCommitString();
     static void resetCommitString();
-    static bool isPrintable(KeyEvent &key);
+    static bool isPrintable(const KeyEvent &key);
 
 protected:
     static WideString text;
diff --git a/honoka/plugins/asciiinput.cpp b/honoka/plugins/asciiinput.cpp
index 1319b5b..0dfc790 100644
--- a/honoka/plugins/asciiinput.cpp
+++ b/honoka/plugins/asciiinput.cpp
@@ -261,7 +261,7 @@
 
     if (autoCommit) {
         if (autoCommitKey.comp(key)) {
-            if (key.get_unicode_code())
+            if (isPrintable(key))
                 setCommitString(text.substr(0,pos) + key.get_unicode_code());
             else setCommitString(text.substr(0,pos));
             reset();
@@ -270,7 +270,7 @@
         }
     }
 
-    if (key.get_unicode_code() && (!key.is_alt_down()) && (!key.is_control_down())) {
+    if (isPrintable(key)) {
         text = text.substr(0,pos) + key.get_unicode_code() + text.substr(pos);
         pos ++;
         return true;
diff --git a/honoka/plugins/kanainput.cpp b/honoka/plugins/kanainput.cpp
index 0605b54..5b2faa1 100644
--- a/honoka/plugins/kanainput.cpp
+++ b/honoka/plugins/kanainput.cpp
@@ -232,7 +232,7 @@
             }
         }
     }
-    if (key.get_unicode_code()) {
+    if (isPrintable(key)) {
         text = text.substr(0,pos) + key.get_unicode_code() + text.substr(pos);
         pos ++;
         return true;
diff --git a/honoka/plugins/nicolainput.cpp b/honoka/plugins/nicolainput.cpp
index d749194..daf780b 100644
--- a/honoka/plugins/nicolainput.cpp
+++ b/honoka/plugins/nicolainput.cpp
@@ -274,7 +274,7 @@
 
     map<KeyEvent,NicolaKey>::iterator it = keymap.find(key);
     if (it == keymap.end()) {
-        if (key.get_unicode_code() && (!key.is_alt_down()) && (!key.is_control_down())) {
+        if (isPrintable(key)) {
             text = text.substr(0,pos) + key.get_unicode_code() + text.substr(pos);
             pos ++;
             return true;