diff --git a/src/output.jl b/src/output.jl
index a8ee5851..9c9efc66 100644
--- a/src/output.jl
+++ b/src/output.jl
@@ -149,6 +149,12 @@ end
 
 # for writing to io streams... first prepare, then callback
 for mime in keys(_mimeformats)
+    @eval function _writemime(io::IO, m, plt::Plot)
+        warn("_writemime is not defined for this backend. m=", string(m))
+    end
+    @eval function _display(plt::Plot)
+        warn("_display is not defined for this backend.")
+    end
     @eval function Base.writemime(io::IO, m::MIME{Symbol($mime)}, plt::Plot)
         prepare_output(plt)
         _writemime(io, m, plt)
@@ -156,7 +162,6 @@ for mime in keys(_mimeformats)
 end
 
 
-
 # ---------------------------------------------------------
 # A backup, if no PNG generation is defined, is to try to make a PDF and use FileIO to convert