diff --git a/cranelift/codegen/src/machinst/abi_impl.rs b/cranelift/codegen/src/machinst/abi_impl.rs
index fdf9409ae5..b90bc7916b 100644
--- a/cranelift/codegen/src/machinst/abi_impl.rs
+++ b/cranelift/codegen/src/machinst/abi_impl.rs
@@ -674,11 +674,12 @@ impl<M: ABIMachineImpl> ABIBody for ABIBodyImpl<M> {
                     _ => ret.push(M::gen_move(dest_reg, from_reg.to_reg(), ty)),
                 };
             }
-            &ABIArg::Stack(off, ty, ext) => {
+            &ABIArg::Stack(off, mut ty, ext) => {
                 let from_bits = ty_bits(ty) as u8;
                 // Trash the from_reg; it should be its last use.
                 match (ext, from_bits) {
                     (ArgumentExtension::Uext, n) | (ArgumentExtension::Sext, n) if n < 64 => {
+                        assert_eq!(RegClass::I64, from_reg.to_reg().get_class());
                         let signed = ext == ArgumentExtension::Sext;
                         ret.push(M::gen_extend(
                             from_reg,
@@ -687,6 +688,8 @@ impl<M: ABIMachineImpl> ABIBody for ABIBodyImpl<M> {
                             from_bits,
                             /* to_bits = */ 64,
                         ));
+                        // Store the extended version.
+                        ty = I64;
                     }
                     _ => {}
                 };
@@ -1083,7 +1086,7 @@ impl<M: ABIMachineImpl> ABICall for ABICallImpl<M> {
             &ABIArg::Reg(reg, ty, _) => {
                 ctx.emit(M::gen_move(Writable::from_reg(reg.to_reg()), from_reg, ty));
             }
-            &ABIArg::Stack(off, ty, ext) => {
+            &ABIArg::Stack(off, mut ty, ext) => {
                 if ext != ir::ArgumentExtension::None && ty_bits(ty) < 64 {
                     assert_eq!(RegClass::I64, from_reg.get_class());
                     let signed = match ext {
@@ -1101,6 +1104,8 @@ impl<M: ABIMachineImpl> ABICall for ABICallImpl<M> {
                         ty_bits(ty) as u8,
                         64,
                     ));
+                    // Store the extended version.
+                    ty = I64;
                 }
                 ctx.emit(M::gen_store_stack(
                     StackAMode::SPOffset(off, ty),
diff --git a/cranelift/filetests/filetests/vcode/aarch64/call.clif b/cranelift/filetests/filetests/vcode/aarch64/call.clif
index 28d75cb36a..cded47dc5b 100644
--- a/cranelift/filetests/filetests/vcode/aarch64/call.clif
+++ b/cranelift/filetests/filetests/vcode/aarch64/call.clif
@@ -63,7 +63,7 @@ block0(v0: i32):
 ; nextln:  ldp fp, lr, [sp], #16
 ; nextln:  ret
 
-function %f3(i32) -> i32 sext {
+function %f5(i32) -> i32 sext {
 block0(v0: i32):
     return v0
 }
@@ -74,3 +74,59 @@ block0(v0: i32):
 ; nextln:  mov sp, fp
 ; nextln:  ldp fp, lr, [sp], #16
 ; nextln:  ret
+
+function %f6(i8) -> i64 {
+    fn0 = %g(i32, i32, i32, i32, i32, i32, i32, i32, i8 sext) -> i64
+
+block0(v0: i8):
+    v1 = iconst.i32 42
+    v2 = call fn0(v1, v1, v1, v1, v1, v1, v1, v1, v0)
+    return v2
+}
+
+; check:  stp fp, lr, [sp, #-16]!
+; nextln:  mov fp, sp
+; nextln:  mov x8, x0
+; nextln:  sub sp, sp, #16
+; nextln:  virtual_sp_offset_adjust 16
+; nextln:  movz x0, #42
+; nextln:  movz x1, #42
+; nextln:  movz x2, #42
+; nextln:  movz x3, #42
+; nextln:  movz x4, #42
+; nextln:  movz x5, #42
+; nextln:  movz x6, #42
+; nextln:  movz x7, #42
+; nextln:  sxtb x8, w8
+; nextln:  stur x8, [sp]
+; nextln:  ldr x16, 8 ; b 12 ; data
+; nextln:  blr x16
+; nextln:  add sp, sp, #16
+; nextln:  virtual_sp_offset_adjust -16
+; nextln:  mov sp, fp
+; nextln:  ldp fp, lr, [sp], #16
+; nextln:  ret
+
+function %f7(i8) -> i32, i32, i32, i32, i32, i32, i32, i32, i8 sext {
+block0(v0: i8):
+    v1 = iconst.i32 42
+    return v1, v1, v1, v1, v1, v1, v1, v1, v0
+}
+
+; check:  stp fp, lr, [sp, #-16]!
+; nextln:  mov fp, sp
+; nextln:  mov x9, x0
+; nextln:  mov x8, x1
+; nextln:  movz x0, #42
+; nextln:  movz x1, #42
+; nextln:  movz x2, #42
+; nextln:  movz x3, #42
+; nextln:  movz x4, #42
+; nextln:  movz x5, #42
+; nextln:  movz x6, #42
+; nextln:  movz x7, #42
+; nextln:  sxtb x9, w9
+; nextln:  stur x9, [x8]
+; nextln:  mov sp, fp
+; nextln:  ldp fp, lr, [sp], #16
+; nextln:  ret