diff --git a/src/julia-syntax.scm b/src/julia-syntax.scm
index 0b099375d97e4..0adfd65f28d5e 100644
--- a/src/julia-syntax.scm
+++ b/src/julia-syntax.scm
@@ -506,9 +506,20 @@
                                                   (not (any (lambda (s)
                                                               (expr-contains-eq (car s) (caddr k)))
                                                             keyword-sparams)))
-                                             `(call (core typeassert)
-                                                    ,rval0
-                                                    ,(caddr k))
+                                             (let ((T (caddr k)))
+                                               `(call (core typeassert)
+                                                      ,rval0
+                                                      ;; work around `ANY` not being a type. if arg type
+                                                      ;; looks like `ANY`, test whether it is `ANY` at run
+                                                      ;; time and if so, substitute `Any`. issue #21510
+                                                      ,(if (or (eq? T 'ANY)
+                                                               (and (globalref? T)
+                                                                    (eq? (caddr T) 'ANY)))
+                                                           `(call (|.| (core Intrinsics) 'select_value)
+                                                                  (call (core ===) ,T (core ANY))
+                                                                  (core Any)
+                                                                  ,T)
+                                                           T)))
                                              rval0)))
                               ;; if kw[ii] == 'k; k = kw[ii+1]::Type; end
                               `(if (comparison ,elt === (quote ,(decl-var k)))
diff --git a/test/keywordargs.jl b/test/keywordargs.jl
index 14199e2bc7a66..5a0abed112104 100644
--- a/test/keywordargs.jl
+++ b/test/keywordargs.jl
@@ -270,3 +270,8 @@ function g21147(f::Tuple{A}, k = 2) where {B,A<:Tuple{B}}
 end
 @test g21147(((1,),)) === Int
 @test g21147(((1,),), 2) === Int
+
+# issue #21510
+f21510(; a::ANY = 2) = a
+@test f21510(a=:b) == :b
+@test f21510() == 2