diff --git a/cranelift/codegen/src/machinst/abi_impl.rs b/cranelift/codegen/src/machinst/abi_impl.rs
index 3ab06f397e..203efe78cd 100644
--- a/cranelift/codegen/src/machinst/abi_impl.rs
+++ b/cranelift/codegen/src/machinst/abi_impl.rs
@@ -1095,12 +1095,28 @@ impl<M: ABIMachineSpec> ABICallee for ABICalleeImpl<M> {
                 assert_eq!(into_regs.len(), slots.len());
                 for (slot, into_reg) in slots.iter().zip(into_regs.regs().iter()) {
                     match slot {
-                        // Extension mode doesn't matter (we're copying out, not in; we
-                        // ignore high bits by convention).
                         &ABIArgSlot::Reg { reg, ty, .. } => {
+                            // Extension mode doesn't matter (we're copying out, not in; we
+                            // ignore high bits by convention).
                             insts.push(M::gen_move(*into_reg, reg.into(), ty));
                         }
-                        &ABIArgSlot::Stack { offset, ty, .. } => {
+                        &ABIArgSlot::Stack {
+                            offset,
+                            ty,
+                            extension,
+                            ..
+                        } => {
+                            // However, we have to respect the extention mode for stack
+                            // slots, or else we grab the wrong bytes on big-endian.
+                            let ext = M::get_ext_mode(self.sig.call_conv, extension);
+                            let ty = match (ext, ty_bits(ty) as u32) {
+                                (ArgumentExtension::Uext, n) | (ArgumentExtension::Sext, n)
+                                    if n < M::word_bits() =>
+                                {
+                                    M::word_type()
+                                }
+                                _ => ty,
+                            };
                             insts.push(M::gen_load_stack(
                                 StackAMode::FPOffset(
                                     M::fp_to_arg_offset(self.call_conv, &self.flags) + offset,
diff --git a/cranelift/filetests/filetests/isa/s390x/call.clif b/cranelift/filetests/filetests/isa/s390x/call.clif
index bd3648316b..3df63e9f65 100644
--- a/cranelift/filetests/filetests/isa/s390x/call.clif
+++ b/cranelift/filetests/filetests/isa/s390x/call.clif
@@ -125,3 +125,61 @@ block0(v0: i64, v1: i64):
 ;   lmg %r14, %r15, 272(%r15)
 ;   br %r14
 
+
+
+function %incoming_args(i64, i32, i32 uext, i32 sext, i16, i16 uext, i16 sext, i8, i8 uext, i8 sext) -> i64 {
+block0(v0: i64, v1: i32, v2: i32, v3: i32, v4: i16, v5: i16, v6: i16, v7: i8, v8: i8, v9: i8):
+    v10 = uextend.i64 v1
+    v11 = uextend.i64 v2
+    v12 = uextend.i64 v3
+    v13 = uextend.i64 v4
+    v14 = uextend.i64 v5
+    v15 = uextend.i64 v6
+    v16 = uextend.i64 v7
+    v17 = uextend.i64 v8
+    v18 = uextend.i64 v9
+    v19 = iadd v0, v10
+    v20 = iadd v11, v12
+    v21 = iadd v13, v14
+    v22 = iadd v15, v16
+    v23 = iadd v17, v18
+    v24 = iadd v19, v20
+    v25 = iadd v21, v22
+    v26 = iadd v23, v24
+    v27 = iadd v25, v26
+    return v27
+}
+
+;   stmg %r7, %r15, 56(%r15)
+;   aghi %r15, -16
+; block0:
+;   stg %r4, 8(%r15)
+;   lgr %r10, %r5
+;   lg %r11, 176(%r15)
+;   lg %r12, 184(%r15)
+;   llgc %r13, 199(%r15)
+;   lg %r8, 200(%r15)
+;   lg %r7, 208(%r15)
+;   llgfr %r4, %r3
+;   lg %r5, 8(%r15)
+;   llgfr %r5, %r5
+;   lgr %r3, %r10
+;   llgfr %r3, %r3
+;   llghr %r9, %r6
+;   llghr %r10, %r11
+;   llghr %r11, %r12
+;   llgcr %r12, %r13
+;   llgcr %r8, %r8
+;   llgcr %r13, %r7
+;   agrk %r4, %r2, %r4
+;   agr %r5, %r3
+;   agrk %r2, %r9, %r10
+;   agrk %r3, %r11, %r12
+;   agr %r8, %r13
+;   agr %r4, %r5
+;   agrk %r5, %r2, %r3
+;   agrk %r4, %r8, %r4
+;   agrk %r2, %r5, %r4
+;   lmg %r7, %r15, 72(%r15)
+;   br %r14
+