diff --git a/src/util/expr.cpp b/src/util/expr.cpp
index 963def60b12..3b480e4bfe2 100644
--- a/src/util/expr.cpp
+++ b/src/util/expr.cpp
@@ -449,7 +449,9 @@ bool exprt::is_zero() const
         assert(false);
       return rat_value.is_zero();
     }
-    else if(type_id==ID_unsignedbv || type_id==ID_signedbv)
+    else if(type_id==ID_unsignedbv ||
+            type_id==ID_signedbv ||
+            type_id==ID_c_bool)
     {
       return constant.value_is_zero_string();
     }