diff --git a/README.md b/README.md
index 9de7aca7a..5f7cbccdc 100644
--- a/README.md
+++ b/README.md
@@ -70,8 +70,6 @@ Currently, the `@compat` macro supports the following syntaxes:
 
 * Three-argument methods `prevind(s,i,n)`, `nextind(s,i,n)` ([#23805]), and `length(s,i,j)` ([#24999]); the latter two replace `chr2ind` and `ind2chr` in Julia 0.7, respectively.
 
-* `Compat.IOBuffer` supporting keyword arguments ([#25873]).
-
 * `Compat.range` supporting positional and keyword arguments flavors ([#25896]), ([#28708]).
 
 * `Compat.mv` and `Compat.cp` with `force` keyword argument ([#26069]).
diff --git a/src/Compat.jl b/src/Compat.jl
index 6a60d1e79..a01c7617d 100644
--- a/src/Compat.jl
+++ b/src/Compat.jl
@@ -76,57 +76,6 @@ end
     end
 end
 
-# https://github.com/JuliaLang/julia/pull/25872
-if VERSION < v"0.7.0-DEV.3734"
-    if isdefined(Base, :open_flags)
-        import Base.open_flags
-    else
-        # copied from Base:
-        function open_flags(; read=nothing, write=nothing, create=nothing, truncate=nothing, append=nothing)
-            if write === true && read !== true && append !== true
-                create   === nothing && (create   = true)
-                truncate === nothing && (truncate = true)
-            end
-            if truncate === true || append === true
-                write  === nothing && (write  = true)
-                create === nothing && (create = true)
-            end
-            write    === nothing && (write    = false)
-            read     === nothing && (read     = !write)
-            create   === nothing && (create   = false)
-            truncate === nothing && (truncate = false)
-            append   === nothing && (append   = false)
-            return (read, write, create, truncate, append)
-        end
-    end
-    function IOBuffer(
-            data::Union{AbstractVector{UInt8},Nothing}=nothing;
-            read::Union{Bool,Nothing}=data === nothing ? true : nothing,
-            write::Union{Bool,Nothing}=data === nothing ? true : nothing,
-            truncate::Union{Bool,Nothing}=data === nothing ? true : nothing,
-            maxsize::Integer=typemax(Int),
-            sizehint::Union{Integer,Nothing}=nothing)
-        flags = open_flags(read=read, write=write, append=nothing, truncate=truncate)
-        if maxsize < 0
-            throw(ArgumentError("negative maxsize: $(maxsize)"))
-        end
-        if data !== nothing
-            if sizehint !== nothing
-                sizehint!(data, sizehint)
-            end
-            buf = Base.IOBuffer(data, flags[1], flags[2], Int(maxsize))
-        else
-            size = sizehint !== nothing ? Int(sizehint) : maxsize != typemax(Int) ? Int(maxsize) : 32
-            buf = Base.IOBuffer(Base.StringVector(size), flags[1], flags[2], Int(maxsize))
-            buf.data[:] = 0
-        end
-        if flags[4] # flags.truncate
-            buf.size = 0
-        end
-        return buf
-    end
-end
-
 @static if VERSION < v"0.7.0-DEV.3986"
     const LinRange = Base.LinSpace
     export LinRange
diff --git a/test/old.jl b/test/old.jl
index 77aa6770d..9025dee09 100644
--- a/test/old.jl
+++ b/test/old.jl
@@ -819,3 +819,18 @@ end
 @test Compat.ceil(pi, digits = 3, base = 2) == 3.25
 @test Compat.round(pi, digits = 3, base = 2) == 3.125
 @test Compat.round(pi, sigdigits = 5, base = 2) == 3.125
+
+# 0.7.0-DEV.3734
+let buf = Compat.IOBuffer(read=true, write=false, maxsize=25)
+    @test buf.readable
+    @test !buf.writable
+    @test buf.maxsize == 25
+end
+let buf = Compat.IOBuffer(zeros(UInt8, 4), write=true) # issue #502
+    write(buf, 'a')
+    @test take!(buf) == [0x61]
+end
+let buf = Compat.IOBuffer(sizehint=20)
+    println(buf, "Hello world.")
+    @test String(take!(buf)) == "Hello world.\n"
+end
diff --git a/test/runtests.jl b/test/runtests.jl
index 6302abe65..13a4f345e 100644
--- a/test/runtests.jl
+++ b/test/runtests.jl
@@ -82,21 +82,6 @@ end
 
 @test codeunit("foo") == codeunit(SubString("fooαβγ",1,3)) == UInt8
 
-# 0.7.0-DEV.3734
-let buf = Compat.IOBuffer(read=true, write=false, maxsize=25)
-    @test buf.readable
-    @test !buf.writable
-    @test buf.maxsize == 25
-end
-let buf = Compat.IOBuffer(zeros(UInt8, 4), write=true) # issue #502
-    write(buf, 'a')
-    @test take!(buf) == [0x61]
-end
-let buf = Compat.IOBuffer(sizehint=20)
-    println(buf, "Hello world.")
-    @test String(take!(buf)) == "Hello world.\n"
-end
-
 # 0.7.0-DEV.3986
 @test_throws ArgumentError Compat.range(1)
 @test_throws ArgumentError Compat.range(nothing)