diff --git a/README.md b/README.md
index 1909c15ac..0001d528a 100644
--- a/README.md
+++ b/README.md
@@ -262,6 +262,8 @@ for `HermOrSym` such that using the new methods are backward compatible.
 
 * Single-argument `min`, `max` and `minmax` are defined on 0.4.
 
+* The `Expr(:macrocall)` has an extra initial argument `__source__`, which can be tested for with `Compat.macros_have_sourceloc`.
+
 ## New types
 
 Currently, no new exported types are introduced by Compat.
diff --git a/src/Compat.jl b/src/Compat.jl
index 8679e7e08..e488371e9 100644
--- a/src/Compat.jl
+++ b/src/Compat.jl
@@ -1494,4 +1494,7 @@ end
 
 include("to-be-deprecated.jl")
 
+# https://github.com/JuliaLang/julia/pull/21746
+const macros_have_sourceloc = VERSION >= v"0.7-" && length(:(@test).args) == 2
+
 end # module Compat