diff --git a/ports/bare-arm/qstrdefsport.h b/ports/bare-arm/qstrdefsport.h
index 3ba897069b..00d3e2ae3c 100644
--- a/ports/bare-arm/qstrdefsport.h
+++ b/ports/bare-arm/qstrdefsport.h
@@ -1 +1,2 @@
 // qstrs specific to this port
+// *FORMAT-OFF*
diff --git a/ports/cc3200/qstrdefsport.h b/ports/cc3200/qstrdefsport.h
index d5f22d70a8..3f613266d2 100644
--- a/ports/cc3200/qstrdefsport.h
+++ b/ports/cc3200/qstrdefsport.h
@@ -25,6 +25,8 @@
  * THE SOFTWARE.
  */
 
+// *FORMAT-OFF*
+
 // for machine module
 Q(/)
 // entries for sys.path
diff --git a/ports/esp32/qstrdefsport.h b/ports/esp32/qstrdefsport.h
index ff6c2cc426..47e22388bc 100644
--- a/ports/esp32/qstrdefsport.h
+++ b/ports/esp32/qstrdefsport.h
@@ -25,6 +25,7 @@
  */
 
 // qstrs specific to this port, only needed if they aren't auto-generated
+// *FORMAT-OFF*
 
 // Entries for sys.path
 Q(/lib)
diff --git a/ports/esp8266/hspi_register.h b/ports/esp8266/hspi_register.h
index 4dd335b400..50ef2fdca3 100644
--- a/ports/esp8266/hspi_register.h
+++ b/ports/esp8266/hspi_register.h
@@ -8,6 +8,8 @@
  *  names of these defines are likely to change.
  */
 
+// *FORMAT-OFF*
+
 #ifndef SPI_REGISTER_H_INCLUDED
 #define SPI_REGISTER_H_INCLUDED
 
diff --git a/ports/esp8266/qstrdefsport.h b/ports/esp8266/qstrdefsport.h
index 8f301a69c5..b84790c66e 100644
--- a/ports/esp8266/qstrdefsport.h
+++ b/ports/esp8266/qstrdefsport.h
@@ -25,6 +25,7 @@
  */
 
 // qstrs specific to this port, only needed if they aren't auto-generated
+// *FORMAT-OFF*
 
 // Entries for sys.path
 Q(/)
diff --git a/ports/javascript/qstrdefsport.h b/ports/javascript/qstrdefsport.h
index 3ba897069b..00d3e2ae3c 100644
--- a/ports/javascript/qstrdefsport.h
+++ b/ports/javascript/qstrdefsport.h
@@ -1 +1,2 @@
 // qstrs specific to this port
+// *FORMAT-OFF*
diff --git a/ports/minimal/qstrdefsport.h b/ports/minimal/qstrdefsport.h
index 3ba897069b..00d3e2ae3c 100644
--- a/ports/minimal/qstrdefsport.h
+++ b/ports/minimal/qstrdefsport.h
@@ -1 +1,2 @@
 // qstrs specific to this port
+// *FORMAT-OFF*
diff --git a/ports/nrf/qstrdefsport.h b/ports/nrf/qstrdefsport.h
index ef398a4c0a..9608dbb247 100644
--- a/ports/nrf/qstrdefsport.h
+++ b/ports/nrf/qstrdefsport.h
@@ -25,6 +25,8 @@
  */
 
 // qstrs specific to this port
+// *FORMAT-OFF*
+
 Q(a)
 Q(a#)
 Q(a#:1)
diff --git a/ports/pic16bit/qstrdefsport.h b/ports/pic16bit/qstrdefsport.h
index 3ba897069b..00d3e2ae3c 100644
--- a/ports/pic16bit/qstrdefsport.h
+++ b/ports/pic16bit/qstrdefsport.h
@@ -1 +1,2 @@
 // qstrs specific to this port
+// *FORMAT-OFF*
diff --git a/ports/powerpc/qstrdefsport.h b/ports/powerpc/qstrdefsport.h
index 3ba897069b..00d3e2ae3c 100644
--- a/ports/powerpc/qstrdefsport.h
+++ b/ports/powerpc/qstrdefsport.h
@@ -1 +1,2 @@
 // qstrs specific to this port
+// *FORMAT-OFF*
diff --git a/ports/qemu-arm/qstrdefsport.h b/ports/qemu-arm/qstrdefsport.h
index 3ba897069b..00d3e2ae3c 100644
--- a/ports/qemu-arm/qstrdefsport.h
+++ b/ports/qemu-arm/qstrdefsport.h
@@ -1 +1,2 @@
 // qstrs specific to this port
+// *FORMAT-OFF*
diff --git a/ports/samd/qstrdefsport.h b/ports/samd/qstrdefsport.h
index 3ba897069b..00d3e2ae3c 100644
--- a/ports/samd/qstrdefsport.h
+++ b/ports/samd/qstrdefsport.h
@@ -1 +1,2 @@
 // qstrs specific to this port
+// *FORMAT-OFF*
diff --git a/ports/stm32/qstrdefsport.h b/ports/stm32/qstrdefsport.h
index 857dc709c9..bc07f2752a 100644
--- a/ports/stm32/qstrdefsport.h
+++ b/ports/stm32/qstrdefsport.h
@@ -25,6 +25,7 @@
  */
 
 // qstrs specific to this port
+// *FORMAT-OFF*
 
 // Entries for sys.path
 Q(/flash)
diff --git a/ports/teensy/qstrdefsport.h b/ports/teensy/qstrdefsport.h
index 3ba897069b..00d3e2ae3c 100644
--- a/ports/teensy/qstrdefsport.h
+++ b/ports/teensy/qstrdefsport.h
@@ -1 +1,2 @@
 // qstrs specific to this port
+// *FORMAT-OFF*
diff --git a/ports/unix/qstrdefsport.h b/ports/unix/qstrdefsport.h
index ebfaa6ccab..8b827a8d64 100644
--- a/ports/unix/qstrdefsport.h
+++ b/ports/unix/qstrdefsport.h
@@ -23,3 +23,5 @@
  * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
  * THE SOFTWARE.
  */
+
+// *FORMAT-OFF*
diff --git a/py/gc.c b/py/gc.c
index c18cd429f3..092dbc750d 100644
--- a/py/gc.c
+++ b/py/gc.c
@@ -473,10 +473,12 @@ void *gc_alloc(size_t n_bytes, unsigned int alloc_flags) {
         n_free = 0;
         for (i = MP_STATE_MEM(gc_last_free_atb_index); i < MP_STATE_MEM(gc_alloc_table_byte_len); i++) {
             byte a = MP_STATE_MEM(gc_alloc_table_start)[i];
+            // *FORMAT-OFF*
             if (ATB_0_IS_FREE(a)) { if (++n_free >= n_blocks) { i = i * BLOCKS_PER_ATB + 0; goto found; } } else { n_free = 0; }
             if (ATB_1_IS_FREE(a)) { if (++n_free >= n_blocks) { i = i * BLOCKS_PER_ATB + 1; goto found; } } else { n_free = 0; }
             if (ATB_2_IS_FREE(a)) { if (++n_free >= n_blocks) { i = i * BLOCKS_PER_ATB + 2; goto found; } } else { n_free = 0; }
             if (ATB_3_IS_FREE(a)) { if (++n_free >= n_blocks) { i = i * BLOCKS_PER_ATB + 3; goto found; } } else { n_free = 0; }
+            // *FORMAT-ON*
         }
 
         GC_EXIT();
diff --git a/py/grammar.h b/py/grammar.h
index ca9b5b379d..c3d30cdf7c 100644
--- a/py/grammar.h
+++ b/py/grammar.h
@@ -24,6 +24,8 @@
  * THE SOFTWARE.
  */
 
+// *FORMAT-OFF*
+
 // rules for writing rules:
 // - zero_or_more is implemented using opt_rule around a one_or_more rule
 // - don't put opt_rule in arguments of or rule; instead, wrap the call to this or rule in opt_rule
diff --git a/py/nlr.h b/py/nlr.h
index 3be3eb58cc..f9fbf56e54 100644
--- a/py/nlr.h
+++ b/py/nlr.h
@@ -42,6 +42,8 @@
 #define MICROPY_NLR_NUM_REGS_XTENSA         (10)
 #define MICROPY_NLR_NUM_REGS_XTENSAWIN      (17)
 
+// *FORMAT-OFF*
+
 // If MICROPY_NLR_SETJMP is not enabled then auto-detect the machine arch
 #if !MICROPY_NLR_SETJMP
 // A lot of nlr-related things need different treatment on Windows
@@ -83,6 +85,8 @@
 #endif
 #endif
 
+// *FORMAT-ON*
+
 #if MICROPY_NLR_SETJMP
 #include <setjmp.h>
 #endif
diff --git a/py/objexcept.c b/py/objexcept.c
index de3b0abe13..b5c1693279 100644
--- a/py/objexcept.c
+++ b/py/objexcept.c
@@ -224,6 +224,8 @@ const mp_obj_type_t mp_type_BaseException = {
     .attr = mp_obj_exception_attr,
 };
 
+// *FORMAT-OFF*
+
 // List of all exceptions, arranged as in the table at:
 // http://docs.python.org/3/library/exceptions.html
 MP_DEFINE_EXCEPTION(SystemExit, BaseException)
@@ -303,6 +305,8 @@ MP_DEFINE_EXCEPTION(Exception, BaseException)
     MP_DEFINE_EXCEPTION(ResourceWarning, Warning)
     */
 
+// *FORMAT-ON*
+
 mp_obj_t mp_obj_new_exception(const mp_obj_type_t *exc_type) {
     assert(exc_type->make_new == mp_obj_exception_make_new);
     return mp_obj_exception_make_new(exc_type, 0, 0, NULL);
diff --git a/py/objint_mpz.c b/py/objint_mpz.c
index 5c014ac23e..7b2bcc9c96 100644
--- a/py/objint_mpz.c
+++ b/py/objint_mpz.c
@@ -41,6 +41,7 @@
 
 #if MICROPY_PY_SYS_MAXSIZE
 // Export value for sys.maxsize
+// *FORMAT-OFF*
 #define DIG_MASK ((MPZ_LONG_1 << MPZ_DIG_SIZE) - 1)
 STATIC const mpz_dig_t maxsize_dig[] = {
     #define NUM_DIG 1
@@ -64,6 +65,7 @@ STATIC const mpz_dig_t maxsize_dig[] = {
      #endif
     #endif
 };
+// *FORMAT-ON*
 const mp_obj_int_t mp_maxsize_obj = {
     {&mp_type_int},
     {.fixed_dig = 1, .len = NUM_DIG, .alloc = NUM_DIG, .dig = (mpz_dig_t*)maxsize_dig}
diff --git a/py/parse.c b/py/parse.c
index 42a947997a..1174f5d83f 100644
--- a/py/parse.c
+++ b/py/parse.c
@@ -58,6 +58,8 @@
 // (un)comment to use rule names; for debugging
 //#define USE_RULE_NAME (1)
 
+// *FORMAT-OFF*
+
 enum {
 // define rules with a compile function
 #define DEF_RULE(rule, comp, kind, ...) RULE_##rule,
@@ -207,6 +209,8 @@ STATIC const char *const rule_name_table[] = {
 };
 #endif
 
+// *FORMAT-ON*
+
 typedef struct _rule_stack_t {
     size_t src_line : (8 * sizeof(size_t) - 8); // maximum bits storing source line number
     size_t rule_id : 8; // this must be large enough to fit largest rule number
diff --git a/py/qstrdefs.h b/py/qstrdefs.h
index 5c8b13b47e..5b4e0dc48e 100644
--- a/py/qstrdefs.h
+++ b/py/qstrdefs.h
@@ -24,6 +24,8 @@
  * THE SOFTWARE.
  */
 
+// *FORMAT-OFF*
+
 #include "py/mpconfig.h"
 
 // All the qstr definitions in this file are available as constants.
diff --git a/py/vm.c b/py/vm.c
index 11dbffaffc..8c835bb9b8 100644
--- a/py/vm.c
+++ b/py/vm.c
@@ -36,6 +36,8 @@
 #include "py/bc.h"
 #include "py/profile.h"
 
+// *FORMAT-OFF*
+
 #if 0
 #define TRACE(ip) printf("sp=%d ", (int)(sp - &code_state->state[0] + 1)); mp_bytecode_print2(ip, 1, code_state->fun_bc->const_table);
 #else
diff --git a/py/vmentrytable.h b/py/vmentrytable.h
index 7f55a4806c..068214bf91 100644
--- a/py/vmentrytable.h
+++ b/py/vmentrytable.h
@@ -24,6 +24,8 @@
  * THE SOFTWARE.
  */
 
+// *FORMAT-OFF*
+
 #if __clang__
 #pragma clang diagnostic push
 #pragma clang diagnostic ignored "-Winitializer-overrides"