diff --git a/base/error.jl b/base/error.jl
index 37ceb39253e38..e25157b6f2b95 100644
--- a/base/error.jl
+++ b/base/error.jl
@@ -223,14 +223,14 @@ macro assert(ex, msgs...)
         msg = msg # pass-through
     elseif !isempty(msgs) && (isa(msg, Expr) || isa(msg, Symbol))
         # message is an expression needing evaluating
-        msg = :(Main.Base.string($(esc(msg))))
+        msg = :(Main.Base.invokelatest(Main.Base.string, $(esc(msg))))
     elseif isdefined(Main, :Base) && isdefined(Main.Base, :string) && applicable(Main.Base.string, msg)
         msg = Main.Base.string(msg)
     else
         # string() might not be defined during bootstrap
         msg = quote
             msg = $(Expr(:quote,msg))
-            isdefined(Main, :Base) ? Main.Base.string(msg) :
+            isdefined(Main, :Base) ? Main.Base.invokelatest(Main.Base.string, msg) :
                 (Core.println(msg); "Error during bootstrap. See stdout.")
         end
     end