diff --git a/src/unix/ibus/ibus_header.h b/src/unix/ibus/ibus_header.h
index 0daa9f183..11a86005e 100644
--- a/src/unix/ibus/ibus_header.h
+++ b/src/unix/ibus/ibus_header.h
@@ -40,8 +40,8 @@ static_assert(std::is_same<guint, uint>::value, "guint must be uint.");
 static_assert(std::is_same<gchar, char>::value, "gchar must be char.");
 static_assert(std::is_same<gboolean, int>::value, "gboolean must be int.");
 
-#if !IBUS_CHECK_VERSION(1, 5, 4)
-#error "ibus-mozc requires IBus>=1.5.4"
-#endif  // libibus (<1.5.4)
+#if !IBUS_CHECK_VERSION(1, 5, 33)
+#error "ibus-mozc requires IBus>=1.5.33"
+#endif  // libibus (<1.5.33)
 
 #endif  // MOZC_UNIX_IBUS_IBUS_HEADER_H_
diff --git a/src/unix/ibus/ibus_wrapper.cc b/src/unix/ibus/ibus_wrapper.cc
index 2c18c004c..b825a6b40 100644
--- a/src/unix/ibus/ibus_wrapper.cc
+++ b/src/unix/ibus/ibus_wrapper.cc
@@ -42,9 +42,9 @@ static_assert(std::is_same<gchar, char>::value, "gchar must be char.");
 static_assert(std::is_same<gboolean, int>::value, "gboolean must be int.");
 static_assert(std::is_same<gpointer, void*>::value, "gpointer must be void*.");
 
-#if !IBUS_CHECK_VERSION(1, 5, 4)
-#error "ibus-mozc requires IBus>=1.5.4"
-#endif  // libibus (<1.5.4)
+#if !IBUS_CHECK_VERSION(1, 5, 33)
+#error "ibus-mozc requires IBus>=1.5.33"
+#endif  // libibus (<1.5.33)
 
 namespace mozc {
 namespace ibus {
diff --git a/src/unix/ibus/preedit_handler.cc b/src/unix/ibus/preedit_handler.cc
index a04f92f14..681aab5ad 100644
--- a/src/unix/ibus/preedit_handler.cc
+++ b/src/unix/ibus/preedit_handler.cc
@@ -55,35 +55,20 @@ IbusTextWrapper ComposePreeditText(const commands::Preedit& preedit) {
     IBusAttrUnderline attr = IBUS_ATTR_UNDERLINE_ERROR;
     switch (segment.annotation()) {
       case commands::Preedit::Segment::NONE:
-        attr = IBUS_ATTR_UNDERLINE_NONE;
+        // No decoration
         break;
       case commands::Preedit::Segment::UNDERLINE:
-        attr = IBUS_ATTR_UNDERLINE_SINGLE;
+        text.AppendAttribute(IBUS_ATTR_TYPE_HINT, IBUS_ATTR_PREEDIT_WHOLE,
+                             start, end);
         break;
       case commands::Preedit::Segment::HIGHLIGHT:
-        attr = IBUS_ATTR_UNDERLINE_DOUBLE;
+        text.AppendAttribute(IBUS_ATTR_TYPE_HINT, IBUS_ATTR_PREEDIT_SELECTION,
+                             start, end);
         break;
       default:
         LOG(ERROR) << "unknown annotation:" << segment.annotation();
         break;
     }
-    end += segment.value_length();
-    text.AppendAttribute(IBUS_ATTR_TYPE_UNDERLINE, attr, start, end);
-
-    // Many applications show a single underline regardless of using
-    // IBUS_ATTR_UNDERLINE_SINGLE or IBUS_ATTR_UNDERLINE_DOUBLE for some
-    // reasons. Here we add a background color for the highlighted candidate
-    // to make it easiliy distinguishable.
-    if (segment.annotation() == commands::Preedit::Segment::HIGHLIGHT) {
-      constexpr uint kBackgroundColor = 0xD1EAFF;
-      text.AppendAttribute(IBUS_ATTR_TYPE_BACKGROUND, kBackgroundColor, start,
-                           end);
-      // IBUS_ATTR_TYPE_FOREGROUND is necessary to highlight the segment on
-      // Firefox.
-      constexpr uint kForegroundColor = 0x000000;
-      text.AppendAttribute(IBUS_ATTR_TYPE_FOREGROUND, kForegroundColor, start,
-                           end);
-    }
     start = end;
   }