diff --git a/README.md b/README.md
index 17f0ebc76..9b5701fb5 100644
--- a/README.md
+++ b/README.md
@@ -109,10 +109,6 @@ Currently, the `@compat` macro supports the following syntaxes:
 
 ## Renaming
 
-* `Compat.indexin` accepts any iterable as first argument, returns `nothing` (rather than `0`)
-   for entries with no match and gives the index of the first (rather than the last) match
-   ([#25662], [#25998]).
-
 * `isupper`, `islower`, `ucfirst` and `lcfirst` are now `isuppercase`, `islowercase`,
   `uppercasefirst` and `lowercasefirst` ([#26442]).
 
diff --git a/src/Compat.jl b/src/Compat.jl
index f056c32e7..e92b2d42d 100644
--- a/src/Compat.jl
+++ b/src/Compat.jl
@@ -76,19 +76,6 @@ end
     end
 end
 
-if VERSION < v"0.7.0-DEV.3972"
-    function indexin(a, b::AbstractArray)
-        inds = keys(b)
-        bdict = Dict{eltype(b),eltype(inds)}()
-        for (val, ind) in zip(b, inds)
-            get!(bdict, val, ind)
-        end
-        return Union{eltype(inds), Nothing}[
-             get(bdict, i, nothing) for i in a
-         ]
-    end
-end
-
 if VERSION < v"0.7.0-DEV.4585"
     export isuppercase, islowercase, uppercasefirst, lowercasefirst
     const isuppercase = isupper
diff --git a/test/old.jl b/test/old.jl
index 8a7d2ef77..62634fc74 100644
--- a/test/old.jl
+++ b/test/old.jl
@@ -864,3 +864,6 @@ mktempdir(@__DIR__) do dir
     end
     @test readdir(dir) == ["dest.jl"]
 end
+
+# 0.7.0-DEV.3972
+@test Compat.indexin([1, 2], [1, 0, 1]) == [1, nothing]
diff --git a/test/runtests.jl b/test/runtests.jl
index 1fae119d4..736bce3e9 100644
--- a/test/runtests.jl
+++ b/test/runtests.jl
@@ -82,9 +82,6 @@ end
 
 @test codeunit("foo") == codeunit(SubString("fooαβγ",1,3)) == UInt8
 
-# 0.7.0-DEV.3972
-@test Compat.indexin([1, 2], [1, 0, 1]) == [1, nothing]
-
 # 0.7.0-DEV.4585
 @test isuppercase('A')
 @test !isuppercase('a')