diff --git a/src/Gnuplot.jl b/src/Gnuplot.jl
index 51920d6..ca3845a 100644
--- a/src/Gnuplot.jl
+++ b/src/Gnuplot.jl
@@ -809,7 +809,7 @@ function useBinaryMethod(args...)
     elseif options.preferred_format == :auto
         if (length(args) == 1)  &&  isa(args[1], AbstractMatrix)
             binary = true
-        elseif all(ndims.(args) .== 1)  &&  all(eltype.(args) .<: Real)
+        elseif all(ndims.(args) .== 1)  &&  all(Base.:<:.(eltype.(args), Real))
             s = sum(length.(args))
             if s > 1e4
                 binary = true