diff --git a/base/iobuffer.jl b/base/iobuffer.jl
index b2e51618a8835..dd3b757c0e3f0 100644
--- a/base/iobuffer.jl
+++ b/base/iobuffer.jl
@@ -771,7 +771,7 @@ function take!(io::IOBuffer)
         elseif io.writable
             data = wrap(Array, memoryref(io.data, io.ptr), nbytes)
         else
-            data = read!(io, data)
+            error("Unreachable IOBuffer state")
         end
     end
     if io.writable