diff --git a/base/deprecated.jl b/base/deprecated.jl
index 8d5b220ef0f82..18ee71a6c1525 100644
--- a/base/deprecated.jl
+++ b/base/deprecated.jl
@@ -539,6 +539,55 @@ end
 
 export MathConst, @math_const
 
+# 11551
+
+macro unexportedwarn(old, new)
+    meta = Expr(:meta, :noinline)
+    if isa(old,Symbol)
+        oldname = Expr(:quote, old)
+        newname = Expr(:quote, new)
+        Expr(:toplevel,
+                :(function $old(args...)
+                $meta
+                depwarn(string("Base.", $oldname, " was undocumented and unexported,\n",
+                "and has been removed.  Use ", $newname, " instead,\n",
+                "however it is also undocumented and unexported, and may change in the future."),
+                $oldname)
+                $new(args...)
+                end))
+    elseif isa(old,Expr) && old.head == :call
+        oldcall = sprint(io->show_unquoted(io,old))
+        newcall = sprint(io->show_unquoted(io,new))
+        oldsym = if isa(old.args[1],Symbol)
+            old.args[1]
+        elseif isa(old.args[1],Expr) && old.args[1].head == :curly
+            old.args[1].args[1]
+        else
+            error("invalid usage of @unexportedwarn")
+        end
+        oldname = Expr(:quote, oldsym)
+        Expr(:toplevel,
+            :($(esc(old)) = begin
+                  $meta
+                  depwarn(string("Base.", $oldcall, " was undocumented and unexported,\n",
+                         "and has been removed.  Use ", $newcall, " instead,\n",
+                         "however it is also undocumented and unexported, and may change in the future."),
+                         $oldname)
+                  $(esc(new))
+              end))
+    else
+        error("invalid usage of @unexportedwarn")
+    end
+end
+
+@unexportedwarn utf16_is_surrogate(ch::Uint16) Base.is_surrogate_codeunit(ch)
+@unexportedwarn utf16_is_lead(ch::UInt16)      Base.is_surrogate_lead(ch)
+@unexportedwarn utf16_is_trail(ch::UInt16)     Base.is_surrogate_trail(ch)
+@unexportedwarn utf16_get_supplementary(lead::UInt16, trail::UInt16) Base.get_supplementary(lead, trail)
+
+@unexportedwarn is_utf8_start(ch::UInt8)         !Base.is_valid_continuation(ch)
+@unexportedwarn is_utf8_continuation(ch::UInt8)  Base.is_valid_continuation(ch)
+
 # 11280, mmap
 
 export msync
diff --git a/test/choosetests.jl b/test/choosetests.jl
index 2a2eecfcbe248..1766fd75ac415 100644
--- a/test/choosetests.jl
+++ b/test/choosetests.jl
@@ -21,7 +21,7 @@ function choosetests(choices = [])
         "arrayops", "tuple", "subarray", "reduce", "reducedim", "random",
         "abstractarray", "intfuncs", "simdloop", "blas", "sparse",
         "bitarray", "copy", "math", "fastmath", "functional",
-        "operators", "path", "ccall", "parse", "loading",
+        "operators", "path", "ccall", "parse", "loading", "deprecated",
         "bigint", "sorting", "statistics", "spawn", "backtrace",
         "priorityqueue", "file", "mmap", "version", "resolve",
         "pollfd", "mpfr", "broadcast", "complex", "socket",
diff --git a/test/deprecated.jl b/test/deprecated.jl
new file mode 100644
index 0000000000000..ec6cc147079aa
--- /dev/null
+++ b/test/deprecated.jl
@@ -0,0 +1,23 @@
+# This file is a part of Julia. License is MIT: http://julialang.org/license
+
+if (Base.JLOptions()).depwarn > 1
+    @test_throws ErrorException Base.utf16_is_surrogate(0xdc00)
+    @test_throws ErrorException Base.utf16_is_lead(0xd800)
+    @test_throws ErrorException Base.utf16_is_trail(0xdc00)
+    @test_throws ErrorException Base.utf16_get_supplementary(0xd800, 0xdc00)
+    @test_throws ErrorException Base.is_utf8_start(0x40)
+    @test_throws ErrorException Base.is_utf8_continuation(0x90)
+else
+    olderr = STDERR
+    try
+        rd, wr = redirect_stderr()
+        @test Base.utf16_is_surrogate(0xdc00)
+        @test Base.utf16_is_lead(0xd800)
+        @test Base.utf16_is_trail(0xdc00)
+        @test Base.utf16_get_supplementary(0xd800, 0xdc00) == 0x10000
+        @test Base.is_utf8_start(0x40)
+        @test Base.is_utf8_continuation(0x90)
+    finally
+        redirect_stderr(olderr)
+    end
+end