diff --git a/src/julia-syntax.scm b/src/julia-syntax.scm
index 8facfca3c3aca..d71c7aff58128 100644
--- a/src/julia-syntax.scm
+++ b/src/julia-syntax.scm
@@ -662,7 +662,10 @@
                       (vals   (list-tail dfl n))
                       (absent (list-tail opt n)) ;; absent arguments
                       (body
-                       (if (any (lambda (defaultv)
+                       (if (any vararg? (butlast vals))
+                         ;; Forbid splat in all but the final default value
+                         (error "invalid \"...\" in non-final positional argument default value")
+                         (if (any (lambda (defaultv)
                                   ;; does any default val expression...
                                   (contains (lambda (e)
                                               ;; contain "e" such that...
@@ -681,7 +684,7 @@
                            ;; otherwise add all
                            `(block
                              ,@prologue
-                             (call ,(arg-name (car req)) ,@(map arg-name (cdr passed)) ,@vals)))))
+                             (call ,(arg-name (car req)) ,@(map arg-name (cdr passed)) ,@vals))))))
                  (method-def-expr- name sp passed body)))
              (iota (length opt)))
       ,(method-def-expr- name sparams overall-argl body rett))))
diff --git a/test/syntax.jl b/test/syntax.jl
index 13dd3e5aca1d6..d43162fbd12c9 100644
--- a/test/syntax.jl
+++ b/test/syntax.jl
@@ -3508,6 +3508,26 @@ let x = 1 => 2
     @test_throws "function Base.=> must be explicitly imported to be extended" @eval a => b = 2
 end
 
+# Splatting in non-final default value (Ref #50518)
+for expr in (quote
+    function g1(a=(1,2)..., b...=3)
+        b
+    end
+end,quote
+    function g2(a=(1,2)..., b=3, c=4)
+        (b, c)
+    end
+end,quote
+    function g3(a=(1,2)..., b=3, c...=4)
+        (b, c)
+    end
+end)
+    let exc = try eval(expr); catch exc; exc end
+        @test isa(exc, ErrorException)
+        @test startswith(exc.msg, "syntax: invalid \"...\" in non-final positional argument default value")
+    end
+end
+
 # Test that bad lowering does not segfault (ref #50518)
 @test_throws ErrorException("syntax: Attempted to use slot marked unused") @eval function funused50518(::Float64)
     $(Symbol("#unused#"))