diff --git a/src/complete.cpp b/src/complete.cpp
index e77d11051..d90b5cdb8 100644
--- a/src/complete.cpp
+++ b/src/complete.cpp
@@ -148,6 +148,7 @@ typedef struct complete_entry_opt
             case option_type_double_long:
                 return 2;
         }
+        assert(0 && "Unreachable");
     }
     
 } complete_entry_opt_t;