diff --git a/src/julia-syntax.scm b/src/julia-syntax.scm
index 7b1a15c559103..ce00f3b7cdb7f 100644
--- a/src/julia-syntax.scm
+++ b/src/julia-syntax.scm
@@ -396,6 +396,8 @@
          (vararg (let ((l (if (null? pargl) '() (last pargl))))
                    (if (or (vararg? l) (varargexpr? l))
                        (list l) '())))
+         ;; positional args with vararg
+         (pargl-all pargl)
          ;; positional args without vararg
          (pargl (if (null? vararg) pargl (butlast pargl)))
          ;; positional args with everything required; for use by the core function
@@ -424,13 +426,7 @@
                            (filter nospecialize-meta? kargl)))
          ;; body statements
          (stmts (cdr body))
-         (positional-sparams
-          (filter (lambda (s)
-                    (let ((name (car s)))
-                      (or (expr-contains-eq name (cons 'list pargl))
-                          (and (pair? vararg) (expr-contains-eq name (car vararg)))
-                          (not (expr-contains-eq name (cons 'list kargl))))))
-                  sparams))
+         (positional-sparams (filter-sparams (cons 'list pargl-all) sparams))
          (keyword-sparams
           (filter (lambda (s)
                     (not (any (lambda (p) (eq? (car p) (car s)))
@@ -462,7 +458,7 @@
 
         ;; call with no keyword args
         ,(method-def-expr-
-          name positional-sparams (append pargl vararg)
+          name positional-sparams pargl-all
           `(block
             ,@(without-generated prologue)
             ,(let (;; call mangled(vals..., [rest_kw,] pargs..., [vararg]...)
@@ -478,9 +474,7 @@
 
         ;; call with unsorted keyword args. this sorts and re-dispatches.
         ,(method-def-expr-
-          name
-          ;; remove sparams that don't occur, to avoid printing the warning twice
-          (filter-sparams (cons 'list argl) positional-sparams)
+          name positional-sparams
           `((|::|
              ;; if there are optional positional args, we need to be able to reference the function name
              ,(if (any kwarg? pargl) (gensy) UNUSED)
diff --git a/test/keywordargs.jl b/test/keywordargs.jl
index 51c6c60e83772..eacacdc2ea248 100644
--- a/test/keywordargs.jl
+++ b/test/keywordargs.jl
@@ -117,6 +117,17 @@ end
     @test kwf7(1.5;k=2.5) === Float64
     @test_throws MethodError kwf7(1.5)
     @test_throws TypeError kwf7(1.5; k=2)
+
+    # issue #30792
+    g30792(a::C; b=R(1)) where {R <: Real, C <: Union{R, Complex{R}}} = R
+    @test g30792(1.0) === Float64
+    @test g30792(1.0im) === Float64
+    @test g30792(1.0im, b=1) === Float64
+    @test_throws MethodError g30792("")
+    f30792(a::C; b::R=R(1)) where {R <: Real, C <: Union{R, Complex{R}}} = R
+    @test f30792(2im) === Int
+    @test f30792(2im, b=3) === Int
+    @test_throws TypeError f30792(2im, b=3.0)
 end
 # try to confuse it with quoted symbol
 kwf8(x::MIME{:T};k::T=0) where {T} = 0