diff --git a/base/compiler/ssair/inlining.jl b/base/compiler/ssair/inlining.jl
index 1dce18bc35393..902c567957eeb 100644
--- a/base/compiler/ssair/inlining.jl
+++ b/base/compiler/ssair/inlining.jl
@@ -492,8 +492,7 @@ function ir_inline_unionsplit!(compact::IncrementalCompact, idx::Int,
     end
 
     # We're now in the join block.
-    compact.ssa_rename[compact.idx-1] = insert_node_here!(compact, pn, typ, line)
-    nothing
+    return insert_node_here!(compact, pn, typ, line)
 end
 
 function batch_inline!(todo::Vector{Pair{Int, Any}}, ir::IRCode, linetable::Vector{LineInfoNode}, propagate_inbounds::Bool)
@@ -548,7 +547,7 @@ function batch_inline!(todo::Vector{Pair{Int, Any}}, ir::IRCode, linetable::Vect
                 if isa(item, InliningTodo)
                     compact.ssa_rename[old_idx] = ir_inline_item!(compact, idx, argexprs, linetable, item, boundscheck, state.todo_bbs)
                 elseif isa(item, UnionSplit)
-                    ir_inline_unionsplit!(compact, idx, argexprs, linetable, item, boundscheck, state.todo_bbs)
+                    compact.ssa_rename[old_idx] = ir_inline_unionsplit!(compact, idx, argexprs, linetable, item, boundscheck, state.todo_bbs)
                 end
                 compact[idx] = nothing
                 refinish && finish_current_bb!(compact, 0)
diff --git a/test/compiler/inline.jl b/test/compiler/inline.jl
index 152aaac50d971..6aa95e242215d 100644
--- a/test/compiler/inline.jl
+++ b/test/compiler/inline.jl
@@ -331,3 +331,11 @@ struct NonIsBitsDimsUndef
 end
 @test Core.Compiler.is_inlineable_constant(NonIsBitsDimsUndef())
 @test !Core.Compiler.is_inlineable_constant((("a"^1000, "b"^1000), nothing))
+
+# Issue #42264 - crash on certain union splits
+let f(x) = (x...,)
+    # Test splatting with a Union of non-{Tuple, SimpleVector} types that require creating new `iterate` calls
+    # in inlining. For this particular case, we're relying on `iterate(::CaretesianIndex)` throwing an error, such
+    # the the original apply call is not union-split, but the inserted `iterate` call is.
+    @test code_typed(f, Tuple{Union{Int64, CartesianIndex{1}, CartesianIndex{3}}})[1][2] == Tuple{Int64}
+end