diff --git a/src/analyze.cpp b/src/analyze.cpp
index 155f017da9..70352a2c18 100644
--- a/src/analyze.cpp
+++ b/src/analyze.cpp
@@ -6369,6 +6369,12 @@ static Error resolve_async_frame(CodeGen *g, ZigType *frame_type) {
                 // This instruction does its own spilling specially, or otherwise doesn't need it.
                 continue;
             }
+            if (instruction->id == IrInstGenIdCast &&
+                reinterpret_cast<IrInstGenCast *>(instruction)->cast_op == CastOpNoop)
+            {
+                // The IR instruction exists only to change the type according to Zig. No spill needed.
+                continue;
+            }
             if (instruction->value->special != ConstValSpecialRuntime)
                 continue;
             if (instruction->base.ref_count == 0)
diff --git a/test/stage1/behavior/async_fn.zig b/test/stage1/behavior/async_fn.zig
index c1e03f62cf..aa0f1f04e2 100644
--- a/test/stage1/behavior/async_fn.zig
+++ b/test/stage1/behavior/async_fn.zig
@@ -1336,7 +1336,7 @@ test "async function passed 0-bit arg after non-0-bit arg" {
         var global_int: i32 = 0;
 
         fn foo() void {
-            _ = async bar(1, .{});
+            bar(1, .{}) catch unreachable;
         }
 
         fn bar(x: i32, args: var) anyerror!void {
@@ -1345,7 +1345,7 @@ test "async function passed 0-bit arg after non-0-bit arg" {
             global_int = x;
         }
     };
-    S.foo();
+    _ = async S.foo();
     resume S.global_frame;
     expect(S.global_int == 1);
 }
@@ -1357,7 +1357,7 @@ test "async function passed align(16) arg after align(8) arg" {
 
         fn foo() void {
             var a: u128 = 99;
-            _ = async bar(10, .{a});
+            bar(10, .{a}) catch unreachable;
         }
 
         fn bar(x: u64, args: var) anyerror!void {
@@ -1367,7 +1367,7 @@ test "async function passed align(16) arg after align(8) arg" {
             global_int = args[0];
         }
     };
-    S.foo();
+    _ = async S.foo();
     resume S.global_frame;
     expect(S.global_int == 99);
 }