diff -ura mozc.orig/src/prediction/zero_query_dict.h mozc/src/prediction/zero_query_dict.h
--- mozc.orig/src/prediction/zero_query_dict.h	2018-05-27 12:14:39.000000000 +0200
+++ mozc/src/prediction/zero_query_dict.h	2018-05-27 12:16:53.158743824 +0200
@@ -132,6 +132,17 @@
       return tmp;
     }
 
+    iterator &operator--() {
+      ptr_ -= kTokenByteSize;
+      return *this;
+    }
+
+    iterator operator--(int) {
+      const iterator tmp(ptr_, string_array_);
+      ptr_ -= kTokenByteSize;
+      return tmp;
+    }
+
     iterator &operator+=(ptrdiff_t n) {
       ptr_ += n * kTokenByteSize;
       return *this;
diff -ura mozc.orig/src/unix/ibus/property_handler.cc mozc/src/unix/ibus/property_handler.cc
--- mozc.orig/src/unix/ibus/property_handler.cc	2018-05-27 12:14:39.000000000 +0200
+++ mozc/src/unix/ibus/property_handler.cc	2018-05-27 12:17:47.877919034 +0200
@@ -80,7 +80,7 @@
 // On IBus 1.4.x, IBus expects that an IME should always be turned on and
 // IME on/off keys are handled by IBus itself rather than each IME.
 #if IBUS_CHECK_VERSION(1, 5, 0)
-const bool kActivatedOnLaunch = false;
+const bool kActivatedOnLaunch = true;
 #else
 const bool kActivatedOnLaunch = true;
 #endif  // IBus>=1.5.0