diff --git a/src/wrapper.jl b/src/wrapper.jl
index 2106d51..1f0681d 100644
--- a/src/wrapper.jl
+++ b/src/wrapper.jl
@@ -180,7 +180,8 @@ function sign!(a::OlmAccount, message)
           a.ptr,
           message, length(message),
           output, siglength)
-    erase!(message)
+    # zero(Char) does not extists, but rand does
+    erase!(message, func = rand)
     String(deepcopy(output))
 end