diff --git a/py/emitnative.c b/py/emitnative.c
index 16f0a08246..504f686bd3 100644
--- a/py/emitnative.c
+++ b/py/emitnative.c
@@ -1391,7 +1391,10 @@ STATIC void emit_native_store_subscr(emit_t *emit) {
         assert(vtype_value == VTYPE_PYOBJ);
         emit_call(emit, MP_F_OBJ_SUBSCR);
     } else {
-        // viper call
+        // viper store
+        // TODO The different machine architectures have very different
+        // capabilities and requirements for stores, so probably best to
+        // write a completely separate store-optimiser for each one.
         stack_info_t *top = peek_stack(emit, 0);
         if (top->vtype == VTYPE_INT && top->kind == STACK_IMM) {
             // index is an immediate
@@ -1402,7 +1405,12 @@ STATIC void emit_native_store_subscr(emit_t *emit) {
             int reg_index = REG_ARG_2;
             int reg_value = REG_ARG_3;
             emit_pre_pop_reg_flexible(emit, &vtype_base, &reg_base, reg_index, reg_value);
+            #if N_X86
+            // special case: x86 needs byte stores to be from lower 4 regs (REG_ARG_3 is EDX)
+            emit_pre_pop_reg(emit, &vtype_value, reg_value);
+            #else
             emit_pre_pop_reg_flexible(emit, &vtype_value, &reg_value, reg_base, reg_index);
+            #endif
             switch (vtype_base) {
                 case VTYPE_PTR8: {
                     // pointer to 8-bit memory
@@ -1449,7 +1457,12 @@ STATIC void emit_native_store_subscr(emit_t *emit) {
             int reg_value = REG_ARG_3;
             emit_pre_pop_reg_flexible(emit, &vtype_index, &reg_index, REG_ARG_1, reg_value);
             emit_pre_pop_reg(emit, &vtype_base, REG_ARG_1);
+            #if N_X86
+            // special case: x86 needs byte stores to be from lower 4 regs (REG_ARG_3 is EDX)
+            emit_pre_pop_reg(emit, &vtype_value, reg_value);
+            #else
             emit_pre_pop_reg_flexible(emit, &vtype_value, &reg_value, REG_ARG_1, reg_index);
+            #endif
             switch (vtype_base) {
                 case VTYPE_PTR8: {
                     // pointer to 8-bit memory
diff --git a/tests/micropython/viper_ptr16_store.py b/tests/micropython/viper_ptr16_store.py
new file mode 100644
index 0000000000..94cde2bc65
--- /dev/null
+++ b/tests/micropython/viper_ptr16_store.py
@@ -0,0 +1,19 @@
+# test ptr16 type
+
+@micropython.viper
+def set(dest:ptr16, val:int):
+    dest[0] = val
+
+@micropython.viper
+def memset(dest:ptr16, val:int, n:int):
+    for i in range(n):
+        dest[i] = val
+
+b = bytearray(4)
+print(b)
+
+set(b, 0x4242)
+print(b)
+
+memset(b, 0x4343, len(b) // 2)
+print(b)
diff --git a/tests/micropython/viper_ptr16_store.py.exp b/tests/micropython/viper_ptr16_store.py.exp
new file mode 100644
index 0000000000..639a43f8f6
--- /dev/null
+++ b/tests/micropython/viper_ptr16_store.py.exp
@@ -0,0 +1,3 @@
+bytearray(b'\x00\x00\x00\x00')
+bytearray(b'BB\x00\x00')
+bytearray(b'CCCC')