diff --git a/mpy-cross/main.c b/mpy-cross/main.c
index a2daf7b22f..6199abd365 100644
--- a/mpy-cross/main.c
+++ b/mpy-cross/main.c
@@ -108,7 +108,6 @@ STATIC int usage(char **argv) {
         "\n"
         "Target specific options:\n"
         "-msmall-int-bits=number : set the maximum bits used to encode a small-int\n"
-        "-mno-unicode : don't support unicode in compiled strings\n"
         "-march=<arch> : set architecture for native emitter; x86, x64, armv6, armv7m, armv7em, armv7emsp, armv7emdp, xtensa, xtensawin\n"
         "\n"
         "Implementation specific options:\n", argv[0]
@@ -203,7 +202,6 @@ MP_NOINLINE int main_(int argc, char **argv) {
 
     // set default compiler configuration
     mp_dynamic_compiler.small_int_bits = 31;
-    mp_dynamic_compiler.py_builtins_str_unicode = 1;
     #if defined(__i386__)
     mp_dynamic_compiler.native_arch = MP_NATIVE_ARCH_X86;
     mp_dynamic_compiler.nlr_buf_num_regs = MICROPY_NLR_NUM_REGS_X86;
@@ -261,10 +259,6 @@ MP_NOINLINE int main_(int argc, char **argv) {
                     return usage(argv);
                 }
                 // TODO check that small_int_bits is within range of host's capabilities
-            } else if (strcmp(argv[a], "-mno-unicode") == 0) {
-                mp_dynamic_compiler.py_builtins_str_unicode = 0;
-            } else if (strcmp(argv[a], "-municode") == 0) {
-                mp_dynamic_compiler.py_builtins_str_unicode = 1;
             } else if (strncmp(argv[a], "-march=", sizeof("-march=") - 1) == 0) {
                 const char *arch = argv[a] + sizeof("-march=") - 1;
                 if (strcmp(arch, "x86") == 0) {
diff --git a/py/lexer.c b/py/lexer.c
index ac406bd469..39e9662f63 100644
--- a/py/lexer.c
+++ b/py/lexer.c
@@ -473,25 +473,23 @@ STATIC void parse_string_literal(mp_lexer_t *lex, bool is_raw, bool is_fstring)
                     }
                 }
                 if (c != MP_LEXER_EOF) {
-                    if (MICROPY_PY_BUILTINS_STR_UNICODE_DYNAMIC) {
-                        if (c < 0x110000 && lex->tok_kind == MP_TOKEN_STRING) {
-                            vstr_add_char(&lex->vstr, c);
-                        } else if (c < 0x100 && lex->tok_kind == MP_TOKEN_BYTES) {
-                            vstr_add_byte(&lex->vstr, c);
-                        } else {
-                            // unicode character out of range
-                            // this raises a generic SyntaxError; could provide more info
-                            lex->tok_kind = MP_TOKEN_INVALID;
-                        }
-                    } else {
-                        // without unicode everything is just added as an 8-bit byte
-                        if (c < 0x100) {
-                            vstr_add_byte(&lex->vstr, c);
-                        } else {
-                            // 8-bit character out of range
-                            // this raises a generic SyntaxError; could provide more info
-                            lex->tok_kind = MP_TOKEN_INVALID;
-                        }
+                    #if MICROPY_PY_BUILTINS_STR_UNICODE
+                    if (c < 0x110000 && lex->tok_kind == MP_TOKEN_STRING) {
+                        // Valid unicode character in a str object.
+                        vstr_add_char(&lex->vstr, c);
+                    } else if (c < 0x100 && lex->tok_kind == MP_TOKEN_BYTES) {
+                        // Valid byte in a bytes object.
+                        vstr_add_byte(&lex->vstr, c);
+                    }
+                    #else
+                    if (c < 0x100) {
+                        // Without unicode everything is just added as an 8-bit byte.
+                        vstr_add_byte(&lex->vstr, c);
+                    }
+                    #endif
+                    else {
+                        // Character out of range; this raises a generic SyntaxError.
+                        lex->tok_kind = MP_TOKEN_INVALID;
                     }
                 }
             } else {
diff --git a/py/mpconfig.h b/py/mpconfig.h
index 8814d1f09c..f9894b497c 100644
--- a/py/mpconfig.h
+++ b/py/mpconfig.h
@@ -429,13 +429,6 @@
 #define MICROPY_DYNAMIC_COMPILER (0)
 #endif
 
-// Configure dynamic compiler macros
-#if MICROPY_DYNAMIC_COMPILER
-#define MICROPY_PY_BUILTINS_STR_UNICODE_DYNAMIC (mp_dynamic_compiler.py_builtins_str_unicode)
-#else
-#define MICROPY_PY_BUILTINS_STR_UNICODE_DYNAMIC MICROPY_PY_BUILTINS_STR_UNICODE
-#endif
-
 // Whether to enable constant folding; eg 1+2 rewritten as 3
 #ifndef MICROPY_COMP_CONST_FOLDING
 #define MICROPY_COMP_CONST_FOLDING (MICROPY_CONFIG_ROM_LEVEL_AT_LEAST_CORE_FEATURES)
diff --git a/py/mpstate.h b/py/mpstate.h
index bc1aaf1e09..98aa9a8498 100644
--- a/py/mpstate.h
+++ b/py/mpstate.h
@@ -55,7 +55,6 @@ enum {
 #if MICROPY_DYNAMIC_COMPILER
 typedef struct mp_dynamic_compiler_t {
     uint8_t small_int_bits; // must be <= host small_int_bits
-    bool py_builtins_str_unicode;
     uint8_t native_arch;
     uint8_t nlr_buf_num_regs;
 } mp_dynamic_compiler_t;
diff --git a/py/persistentcode.h b/py/persistentcode.h
index 37263f66b3..55428e73a6 100644
--- a/py/persistentcode.h
+++ b/py/persistentcode.h
@@ -42,15 +42,11 @@
 #define MPY_FEATURE_DECODE_ARCH(feat) ((feat) >> 2)
 
 // The feature flag bits encode the compile-time config options that affect
-// the generate bytecode. Note: position 0 is now unused
-// (formerly MICROPY_OPT_CACHE_MAP_LOOKUP_IN_BYTECODE).
-#define MPY_FEATURE_FLAGS ( \
-    ((MICROPY_PY_BUILTINS_STR_UNICODE) << 1) \
-    )
+// the generate bytecode. Note: no longer used.
+// (formerly MICROPY_OPT_CACHE_MAP_LOOKUP_IN_BYTECODE and MICROPY_PY_BUILTINS_STR_UNICODE).
+#define MPY_FEATURE_FLAGS (0)
 // This is a version of the flags that can be configured at runtime.
-#define MPY_FEATURE_FLAGS_DYNAMIC ( \
-    ((MICROPY_PY_BUILTINS_STR_UNICODE_DYNAMIC) << 1) \
-    )
+#define MPY_FEATURE_FLAGS_DYNAMIC (0)
 
 // Define the host architecture
 #if MICROPY_EMIT_X86
diff --git a/tests/micropython/import_mpy_native_gc.py b/tests/micropython/import_mpy_native_gc.py
index 44f5942697..a2012fc1cf 100644
--- a/tests/micropython/import_mpy_native_gc.py
+++ b/tests/micropython/import_mpy_native_gc.py
@@ -49,14 +49,14 @@ class UserFS:
 # by the required value of sys.implementation._mpy.
 features0_file_contents = {
     # -march=x64
-    0xA06: b'M\x06\n\x1f\x01\x004build/features0.native.mpy\x00\x8aB\xe9/\x00\x00\x00SH\x8b\x1d\x83\x00\x00\x00\xbe\x02\x00\x00\x00\xffS\x18\xbf\x01\x00\x00\x00H\x85\xc0u\x0cH\x8bC \xbe\x02\x00\x00\x00[\xff\xe0H\x0f\xaf\xf8H\xff\xc8\xeb\xe6ATUSH\x8b\x1dQ\x00\x00\x00H\x8bG\x08L\x8bc(H\x8bx\x08A\xff\xd4H\x8d5+\x00\x00\x00H\x89\xc5H\x8b\x059\x00\x00\x00\x0f\xb78\xffShH\x89\xefA\xff\xd4H\x8b\x03[]A\\\xc3\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x05\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\xa0\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x01\x85\x00\x12factorial\x00\x10\r$\x01&\x9f \x01"\xff',
+    0x806: b'M\x06\b\x1f\x01\x004build/features0.native.mpy\x00\x8aB\xe9/\x00\x00\x00SH\x8b\x1d\x83\x00\x00\x00\xbe\x02\x00\x00\x00\xffS\x18\xbf\x01\x00\x00\x00H\x85\xc0u\x0cH\x8bC \xbe\x02\x00\x00\x00[\xff\xe0H\x0f\xaf\xf8H\xff\xc8\xeb\xe6ATUSH\x8b\x1dQ\x00\x00\x00H\x8bG\x08L\x8bc(H\x8bx\x08A\xff\xd4H\x8d5+\x00\x00\x00H\x89\xc5H\x8b\x059\x00\x00\x00\x0f\xb78\xffShH\x89\xefA\xff\xd4H\x8b\x03[]A\\\xc3\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x05\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\xa0\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x01\x85\x00\x12factorial\x00\x10\r$\x01&\x9f \x01"\xff',
     # -march=armv7m
-    0x1606: b"M\x06\x16\x1f\x01\x004build/features0.native.mpy\x00\x88B\x1a\xe0\x00\x00\x13\xb5\nK\nJ{D\x9cX\x02!\xe3h\x98G\x03F\x01 3\xb9\x02!#i\x01\x93\x02\xb0\xbd\xe8\x10@\x18GXC\x01;\xf4\xe7\x00\xbfn\x00\x00\x00\x00\x00\x00\x00\xf8\xb5\nN\nK~D\xf4XChgiXh\xb8G\x05F\x07K\x08I\xf2XyD\x10\x88ck\x98G(F\xb8G h\xf8\xbd\x00\xbf:\x00\x00\x00\x00\x00\x00\x00\x04\x00\x00\x00\x1e\x00\x00\x00\x00\x00\x00\x00\x05\x00\x00\x00\x00\x00\x00\x00\x84\x00\x00\x00\x00\x00\x00\x00\x01\x84\x10\x12factorial\x00\x10\r>\x01@\x9f:\x01<\xff",
+    0x1406: b"M\x06\x14\x1f\x01\x004build/features0.native.mpy\x00\x88B\x1a\xe0\x00\x00\x13\xb5\nK\nJ{D\x9cX\x02!\xe3h\x98G\x03F\x01 3\xb9\x02!#i\x01\x93\x02\xb0\xbd\xe8\x10@\x18GXC\x01;\xf4\xe7\x00\xbfn\x00\x00\x00\x00\x00\x00\x00\xf8\xb5\nN\nK~D\xf4XChgiXh\xb8G\x05F\x07K\x08I\xf2XyD\x10\x88ck\x98G(F\xb8G h\xf8\xbd\x00\xbf:\x00\x00\x00\x00\x00\x00\x00\x04\x00\x00\x00\x1e\x00\x00\x00\x00\x00\x00\x00\x05\x00\x00\x00\x00\x00\x00\x00\x84\x00\x00\x00\x00\x00\x00\x00\x01\x84\x10\x12factorial\x00\x10\r>\x01@\x9f:\x01<\xff",
 }
 
 # Populate other armv7m-derived archs based on armv7m.
-for arch in (0x1A06, 0x1E06, 0x2206):
-    features0_file_contents[arch] = features0_file_contents[0x1606]
+for arch in (0x1806, 0x1C06, 0x2006):
+    features0_file_contents[arch] = features0_file_contents[0x1406]
 
 if sys.implementation._mpy not in features0_file_contents:
     print("SKIP")
diff --git a/tests/micropython/import_mpy_native_x64.py b/tests/micropython/import_mpy_native_x64.py
index 3a25df1866..453d81f256 100644
--- a/tests/micropython/import_mpy_native_x64.py
+++ b/tests/micropython/import_mpy_native_x64.py
@@ -52,11 +52,11 @@ class UserFS:
 # fmt: off
 user_files = {
     # bad architecture
-    '/mod0.mpy': b'M\x06\xfe\x00\x10',
+    '/mod0.mpy': b'M\x06\xfc\x00\x10',
 
     # test loading of viper and asm
     '/mod1.mpy': (
-        b'M\x06\x0a\x1f' # header
+        b'M\x06\x08\x1f' # header
 
         b'\x02' # n_qstr
         b'\x00' # n_obj
@@ -85,7 +85,7 @@ user_files = {
 
     # test loading viper with additional scope flags and relocation
     '/mod2.mpy': (
-        b'M\x06\x0a\x1f' # header
+        b'M\x06\x08\x1f' # header
 
         b'\x02' # n_qstr
         b'\x00' # n_obj
diff --git a/tools/mpy_ld.py b/tools/mpy_ld.py
index a0817500e6..6189491518 100755
--- a/tools/mpy_ld.py
+++ b/tools/mpy_ld.py
@@ -48,7 +48,6 @@ MP_CODE_NATIVE_VIPER = 4
 MP_SCOPE_FLAG_VIPERRELOC = 0x10
 MP_SCOPE_FLAG_VIPERRODATA = 0x20
 MP_SCOPE_FLAG_VIPERBSS = 0x40
-MICROPY_PY_BUILTINS_STR_UNICODE = 2
 MP_SMALL_INT_BITS = 31
 
 # ELF constants
@@ -116,7 +115,7 @@ class ArchData:
 ARCH_DATA = {
     "x86": ArchData(
         "EM_386",
-        MP_NATIVE_ARCH_X86 << 2 | MICROPY_PY_BUILTINS_STR_UNICODE,
+        MP_NATIVE_ARCH_X86 << 2,
         2,
         4,
         (R_386_PC32, R_386_GOT32, R_386_GOT32X),
@@ -124,7 +123,7 @@ ARCH_DATA = {
     ),
     "x64": ArchData(
         "EM_X86_64",
-        MP_NATIVE_ARCH_X64 << 2 | MICROPY_PY_BUILTINS_STR_UNICODE,
+        MP_NATIVE_ARCH_X64 << 2,
         2,
         8,
         (R_X86_64_GOTPCREL, R_X86_64_REX_GOTPCRELX),
@@ -132,7 +131,7 @@ ARCH_DATA = {
     ),
     "armv7m": ArchData(
         "EM_ARM",
-        MP_NATIVE_ARCH_ARMV7M << 2 | MICROPY_PY_BUILTINS_STR_UNICODE,
+        MP_NATIVE_ARCH_ARMV7M << 2,
         2,
         4,
         (R_ARM_GOT_BREL,),
@@ -140,7 +139,7 @@ ARCH_DATA = {
     ),
     "armv7emsp": ArchData(
         "EM_ARM",
-        MP_NATIVE_ARCH_ARMV7EMSP << 2 | MICROPY_PY_BUILTINS_STR_UNICODE,
+        MP_NATIVE_ARCH_ARMV7EMSP << 2,
         2,
         4,
         (R_ARM_GOT_BREL,),
@@ -148,7 +147,7 @@ ARCH_DATA = {
     ),
     "armv7emdp": ArchData(
         "EM_ARM",
-        MP_NATIVE_ARCH_ARMV7EMDP << 2 | MICROPY_PY_BUILTINS_STR_UNICODE,
+        MP_NATIVE_ARCH_ARMV7EMDP << 2,
         2,
         4,
         (R_ARM_GOT_BREL,),
@@ -156,7 +155,7 @@ ARCH_DATA = {
     ),
     "xtensa": ArchData(
         "EM_XTENSA",
-        MP_NATIVE_ARCH_XTENSA << 2 | MICROPY_PY_BUILTINS_STR_UNICODE,
+        MP_NATIVE_ARCH_XTENSA << 2,
         2,
         4,
         (R_XTENSA_32, R_XTENSA_PLT),
@@ -164,7 +163,7 @@ ARCH_DATA = {
     ),
     "xtensawin": ArchData(
         "EM_XTENSA",
-        MP_NATIVE_ARCH_XTENSAWIN << 2 | MICROPY_PY_BUILTINS_STR_UNICODE,
+        MP_NATIVE_ARCH_XTENSAWIN << 2,
         4,
         4,
         (R_XTENSA_32, R_XTENSA_PLT),