diff --git a/extmod/moduasyncio.c b/extmod/moduasyncio.c
index 01ec582946..0b15c9e079 100644
--- a/extmod/moduasyncio.c
+++ b/extmod/moduasyncio.c
@@ -173,7 +173,7 @@ STATIC mp_obj_t task_cancel(mp_obj_t self_in) {
     // Can't cancel self (not supported yet).
     mp_obj_t cur_task = mp_obj_dict_get(uasyncio_context, MP_OBJ_NEW_QSTR(MP_QSTR_cur_task));
     if (self_in == cur_task) {
-        mp_raise_msg(&mp_type_RuntimeError, MP_ERROR_TEXT("cannot cancel self"));
+        mp_raise_msg(&mp_type_RuntimeError, MP_ERROR_TEXT("can't cancel self"));
     }
     // If Task waits on another task then forward the cancel to the one it's waiting on.
     while (mp_obj_is_subclass_fast(MP_OBJ_FROM_PTR(mp_obj_get_type(self->data)), MP_OBJ_FROM_PTR(&task_type))) {
diff --git a/extmod/moductypes.c b/extmod/moductypes.c
index 59da5f91e7..a7a905c661 100644
--- a/extmod/moductypes.c
+++ b/extmod/moductypes.c
@@ -226,7 +226,7 @@ STATIC mp_uint_t uctypes_struct_size(mp_obj_t desc_in, int layout_type, mp_uint_
             // but scalar structure field is lowered into native Python int, so all
             // type info is lost. So, we cannot say if it's scalar type description,
             // or such lowered scalar.
-            mp_raise_TypeError(MP_ERROR_TEXT("Cannot unambiguously get sizeof scalar"));
+            mp_raise_TypeError(MP_ERROR_TEXT("can't unambiguously get sizeof scalar"));
         }
         syntax_error();
     }
@@ -557,7 +557,7 @@ STATIC mp_obj_t uctypes_struct_subscr(mp_obj_t self_in, mp_obj_t index_in, mp_ob
     } else {
         // load / store
         if (!mp_obj_is_type(self->desc, &mp_type_tuple)) {
-            mp_raise_TypeError(MP_ERROR_TEXT("struct: cannot index"));
+            mp_raise_TypeError(MP_ERROR_TEXT("struct: can't index"));
         }
 
         mp_obj_tuple_t *t = MP_OBJ_TO_PTR(self->desc);
diff --git a/extmod/modure.c b/extmod/modure.c
index ed16955ae4..ff99e66d85 100644
--- a/extmod/modure.c
+++ b/extmod/modure.c
@@ -235,7 +235,7 @@ STATIC mp_obj_t re_split(size_t n_args, const mp_obj_t *args) {
         mp_obj_t s = mp_obj_new_str_of_type(str_type, (const byte *)subj.begin, caps[0] - subj.begin);
         mp_obj_list_append(retval, s);
         if (self->re.sub > 0) {
-            mp_raise_NotImplementedError(MP_ERROR_TEXT("Splitting with sub-captures"));
+            mp_raise_NotImplementedError(MP_ERROR_TEXT("splitting with sub-captures"));
         }
         subj.begin = caps[1];
         if (maxsplit > 0 && --maxsplit == 0) {
@@ -403,7 +403,7 @@ STATIC mp_obj_t mod_re_compile(size_t n_args, const mp_obj_t *args) {
     int error = re1_5_compilecode(&o->re, re_str);
     if (error != 0) {
     error:
-        mp_raise_ValueError(MP_ERROR_TEXT("Error in regex"));
+        mp_raise_ValueError(MP_ERROR_TEXT("error in regex"));
     }
     #if MICROPY_PY_URE_DEBUG
     if (flags & FLAG_DEBUG) {
diff --git a/ports/esp32/machine_adc.c b/ports/esp32/machine_adc.c
index d23e622091..811a208e6d 100644
--- a/ports/esp32/machine_adc.c
+++ b/ports/esp32/machine_adc.c
@@ -81,7 +81,7 @@ STATIC mp_obj_t madc_make_new(const mp_obj_type_t *type, size_t n_args, size_t n
     if (err == ESP_OK) {
         return MP_OBJ_FROM_PTR(self);
     }
-    mp_raise_ValueError(MP_ERROR_TEXT("Parameter Error"));
+    mp_raise_ValueError(MP_ERROR_TEXT("parameter error"));
 }
 
 STATIC void madc_print(const mp_print_t *print, mp_obj_t self_in, mp_print_kind_t kind) {
@@ -104,7 +104,7 @@ STATIC mp_obj_t madc_read(mp_obj_t self_in) {
     madc_obj_t *self = self_in;
     int val = adc1_get_raw(self->adc1_id);
     if (val == -1) {
-        mp_raise_ValueError(MP_ERROR_TEXT("Parameter Error"));
+        mp_raise_ValueError(MP_ERROR_TEXT("parameter error"));
     }
     return MP_OBJ_NEW_SMALL_INT(val);
 }
@@ -117,7 +117,7 @@ STATIC mp_obj_t madc_atten(mp_obj_t self_in, mp_obj_t atten_in) {
     if (err == ESP_OK) {
         return mp_const_none;
     }
-    mp_raise_ValueError(MP_ERROR_TEXT("Parameter Error"));
+    mp_raise_ValueError(MP_ERROR_TEXT("parameter error"));
 }
 MP_DEFINE_CONST_FUN_OBJ_2(madc_atten_obj, madc_atten);
 
@@ -125,7 +125,7 @@ STATIC mp_obj_t madc_width(mp_obj_t cls_in, mp_obj_t width_in) {
     adc_bits_width_t width = mp_obj_get_int(width_in);
     esp_err_t err = adc1_config_width(width);
     if (err != ESP_OK) {
-        mp_raise_ValueError(MP_ERROR_TEXT("Parameter Error"));
+        mp_raise_ValueError(MP_ERROR_TEXT("parameter error"));
     }
     switch (width) {
         case ADC_WIDTH_9Bit:
diff --git a/ports/esp32/machine_dac.c b/ports/esp32/machine_dac.c
index a1a91167a7..02855fcf80 100644
--- a/ports/esp32/machine_dac.c
+++ b/ports/esp32/machine_dac.c
@@ -70,7 +70,7 @@ STATIC mp_obj_t mdac_make_new(const mp_obj_type_t *type, size_t n_args, size_t n
     if (err == ESP_OK) {
         return MP_OBJ_FROM_PTR(self);
     }
-    mp_raise_ValueError(MP_ERROR_TEXT("Parameter Error"));
+    mp_raise_ValueError(MP_ERROR_TEXT("parameter error"));
 }
 
 STATIC void mdac_print(const mp_print_t *print, mp_obj_t self_in, mp_print_kind_t kind) {
@@ -82,14 +82,14 @@ STATIC mp_obj_t mdac_write(mp_obj_t self_in, mp_obj_t value_in) {
     mdac_obj_t *self = self_in;
     int value = mp_obj_get_int(value_in);
     if (value < 0 || value > 255) {
-        mp_raise_ValueError(MP_ERROR_TEXT("Value out of range"));
+        mp_raise_ValueError(MP_ERROR_TEXT("value out of range"));
     }
 
     esp_err_t err = dac_output_voltage(self->dac_id, value);
     if (err == ESP_OK) {
         return mp_const_none;
     }
-    mp_raise_ValueError(MP_ERROR_TEXT("Parameter Error"));
+    mp_raise_ValueError(MP_ERROR_TEXT("parameter error"));
 }
 MP_DEFINE_CONST_FUN_OBJ_2(mdac_write_obj, mdac_write);
 
diff --git a/ports/esp32/machine_pwm.c b/ports/esp32/machine_pwm.c
index c0eae3d0b8..7592f243b7 100644
--- a/ports/esp32/machine_pwm.c
+++ b/ports/esp32/machine_pwm.c
@@ -173,7 +173,7 @@ STATIC void esp32_pwm_init_helper(esp32_pwm_obj_t *self,
     if (tval != -1) {
         if (tval != timer_cfg.freq_hz) {
             if (!set_freq(tval)) {
-                mp_raise_msg_varg(&mp_type_ValueError, MP_ERROR_TEXT("Bad frequency %d"), tval);
+                mp_raise_msg_varg(&mp_type_ValueError, MP_ERROR_TEXT("bad frequency %d"), tval);
             }
         }
     }
@@ -247,7 +247,7 @@ STATIC mp_obj_t esp32_pwm_freq(size_t n_args, const mp_obj_t *args) {
     // set
     int tval = mp_obj_get_int(args[1]);
     if (!set_freq(tval)) {
-        mp_raise_msg_varg(&mp_type_ValueError, MP_ERROR_TEXT("Bad frequency %d"), tval);
+        mp_raise_msg_varg(&mp_type_ValueError, MP_ERROR_TEXT("bad frequency %d"), tval);
     }
     return mp_const_none;
 }
diff --git a/ports/esp32/machine_sdcard.c b/ports/esp32/machine_sdcard.c
index 2c2f3bc4cd..6383728ced 100644
--- a/ports/esp32/machine_sdcard.c
+++ b/ports/esp32/machine_sdcard.c
@@ -177,7 +177,7 @@ STATIC mp_obj_t machine_sdcard_make_new(const mp_obj_type_t *type, size_t n_args
 
     int slot_num = arg_vals[ARG_slot].u_int;
     if (slot_num < 0 || slot_num > 3) {
-        mp_raise_ValueError(MP_ERROR_TEXT("Slot number must be between 0 and 3 inclusive"));
+        mp_raise_ValueError(MP_ERROR_TEXT("slot number must be between 0 and 3 inclusive"));
     }
 
     // Slots 0 and 1 are native SD/MMC, slots 2 and 3 are SPI
@@ -253,7 +253,7 @@ STATIC mp_obj_t machine_sdcard_make_new(const mp_obj_type_t *type, size_t n_args
         if (width == 1 || width == 4 || (width == 8 && slot_num == 0)) {
             slot_config.width = width;
         } else {
-            mp_raise_ValueError(MP_ERROR_TEXT("Width must be 1 or 4 (or 8 on slot 0)"));
+            mp_raise_ValueError(MP_ERROR_TEXT("width must be 1 or 4 (or 8 on slot 0)"));
         }
 
         DEBUG_printf("  Calling init_slot()");
diff --git a/ports/nrf/boards/microbit/modules/microbitimage.c b/ports/nrf/boards/microbit/modules/microbitimage.c
index 56bd18c6ed..d697a9081f 100644
--- a/ports/nrf/boards/microbit/modules/microbitimage.c
+++ b/ports/nrf/boards/microbit/modules/microbitimage.c
@@ -351,7 +351,7 @@ mp_obj_t microbit_image_get_pixel(mp_obj_t self_in, mp_obj_t x_in, mp_obj_t y_in
     mp_int_t x = mp_obj_get_int(x_in);
     mp_int_t y = mp_obj_get_int(y_in);
     if (x < 0 || y < 0) {
-        mp_raise_ValueError(MP_ERROR_TEXT("index cannot be negative"));
+        mp_raise_ValueError(MP_ERROR_TEXT("index can't be negative"));
     }
     if (x < imageWidth(self) && y < imageHeight(self)) {
         return MP_OBJ_NEW_SMALL_INT(imageGetPixelValue(self, x, y));
@@ -363,7 +363,7 @@ MP_DEFINE_CONST_FUN_OBJ_3(microbit_image_get_pixel_obj, microbit_image_get_pixel
 /* Raise an exception if not mutable */
 static void check_mutability(microbit_image_obj_t *self) {
     if (self->base.five) {
-        mp_raise_TypeError(MP_ERROR_TEXT("image cannot be modified (try copying first)"));
+        mp_raise_TypeError(MP_ERROR_TEXT("image can't be modified (try copying first)"));
     }
 }
 
@@ -375,7 +375,7 @@ mp_obj_t microbit_image_set_pixel(mp_uint_t n_args, const mp_obj_t *args) {
     mp_int_t x = mp_obj_get_int(args[1]);
     mp_int_t y = mp_obj_get_int(args[2]);
     if (x < 0 || y < 0) {
-        mp_raise_ValueError(MP_ERROR_TEXT("index cannot be negative"));
+        mp_raise_ValueError(MP_ERROR_TEXT("index can't be negative"));
     }
     mp_int_t bright = mp_obj_get_int(args[3]);
     if (bright < 0 || bright > MAX_BRIGHTNESS)
@@ -416,7 +416,7 @@ mp_obj_t microbit_image_blit(mp_uint_t n_args, const mp_obj_t *args) {
     mp_int_t w = mp_obj_get_int(args[4]);
     mp_int_t h = mp_obj_get_int(args[5]);
     if (w < 0 || h < 0) {
-        mp_raise_ValueError(MP_ERROR_TEXT("size cannot be negative"));
+        mp_raise_ValueError(MP_ERROR_TEXT("size can't be negative"));
     }
     mp_int_t xdest;
     mp_int_t ydest;
diff --git a/ports/stm32/pyb_i2c.c b/ports/stm32/pyb_i2c.c
index 2dbcea2d12..4f8f7a0e37 100644
--- a/ports/stm32/pyb_i2c.c
+++ b/ports/stm32/pyb_i2c.c
@@ -200,7 +200,7 @@ STATIC void i2c_set_baudrate(I2C_InitTypeDef *init, uint32_t baudrate) {
             return;
         }
     }
-    mp_raise_msg_varg(&mp_type_ValueError, MP_ERROR_TEXT("Unsupported I2C baudrate: %u"), baudrate);
+    mp_raise_msg_varg(&mp_type_ValueError, MP_ERROR_TEXT("unsupported I2C baudrate: %u"), baudrate);
 }
 
 uint32_t pyb_i2c_get_baudrate(I2C_HandleTypeDef *i2c) {
diff --git a/ports/unix/modffi.c b/ports/unix/modffi.c
index 1c357652d5..5f9db20325 100644
--- a/ports/unix/modffi.c
+++ b/ports/unix/modffi.c
@@ -148,7 +148,7 @@ STATIC ffi_type *get_ffi_type(mp_obj_t o_in) {
     }
     // TODO: Support actual libffi type objects
 
-    mp_raise_TypeError(MP_ERROR_TEXT("Unknown type"));
+    mp_raise_TypeError(MP_ERROR_TEXT("unknown type"));
 }
 
 STATIC mp_obj_t return_ffi_value(ffi_arg val, char type) {
@@ -218,7 +218,7 @@ STATIC mp_obj_t make_func(mp_obj_t rettype_in, void *func, mp_obj_t argtypes_in)
 
     int res = ffi_prep_cif(&o->cif, FFI_DEFAULT_ABI, nparams, char2ffi_type(*rettype), o->params);
     if (res != FFI_OK) {
-        mp_raise_ValueError(MP_ERROR_TEXT("Error in ffi_prep_cif"));
+        mp_raise_ValueError(MP_ERROR_TEXT("error in ffi_prep_cif"));
     }
 
     return MP_OBJ_FROM_PTR(o);
@@ -276,7 +276,7 @@ STATIC mp_obj_t mod_ffi_callback(mp_obj_t rettype_in, mp_obj_t func_in, mp_obj_t
 
     int res = ffi_prep_cif(&o->cif, FFI_DEFAULT_ABI, nparams, char2ffi_type(*rettype), o->params);
     if (res != FFI_OK) {
-        mp_raise_ValueError(MP_ERROR_TEXT("Error in ffi_prep_cif"));
+        mp_raise_ValueError(MP_ERROR_TEXT("error in ffi_prep_cif"));
     }
 
     res = ffi_prep_closure_loc(o->clo, &o->cif, call_py_func, MP_OBJ_TO_PTR(func_in), o->func);
@@ -425,7 +425,7 @@ STATIC mp_obj_t ffifunc_call(mp_obj_t self_in, size_t n_args, size_t n_kw, const
     }
 
 error:
-    mp_raise_TypeError(MP_ERROR_TEXT("Don't know how to pass object to native function"));
+    mp_raise_TypeError(MP_ERROR_TEXT("don't know how to pass object to native function"));
 }
 
 STATIC const mp_obj_type_t ffifunc_type = {
diff --git a/ports/unix/modjni.c b/ports/unix/modjni.c
index 73c5856a09..a3e3dc21be 100644
--- a/ports/unix/modjni.c
+++ b/ports/unix/modjni.c
@@ -531,7 +531,7 @@ STATIC mp_obj_t call_method(jobject obj, const char *name, jarray methods, bool
                     ret = new_jobject(res);
                 } else {
                     JJ(ReleaseStringUTFChars, name_o, decl);
-                    mp_raise_TypeError(MP_ERROR_TEXT("cannot handle return type"));
+                    mp_raise_TypeError(MP_ERROR_TEXT("can't handle return type"));
                 }
 
                 JJ(ReleaseStringUTFChars, name_o, decl);
diff --git a/py/builtinimport.c b/py/builtinimport.c
index 5c82c68d9f..28a8f41f75 100644
--- a/py/builtinimport.c
+++ b/py/builtinimport.c
@@ -313,7 +313,7 @@ mp_obj_t mp_builtin___import__(size_t n_args, const mp_obj_t *args) {
 
         // We must have some component left over to import from
         if (p == this_name) {
-            mp_raise_ValueError(MP_ERROR_TEXT("cannot perform relative import"));
+            mp_raise_ValueError(MP_ERROR_TEXT("can't perform relative import"));
         }
 
         uint new_mod_l = (mod_len == 0 ? (size_t)(p - this_name) : (size_t)(p - this_name) + 1 + mod_len);
diff --git a/py/objslice.c b/py/objslice.c
index 290c29150e..c65c30601b 100644
--- a/py/objslice.c
+++ b/py/objslice.c
@@ -124,7 +124,7 @@ void mp_obj_slice_indices(mp_obj_t self_in, mp_int_t length, mp_bound_slice_t *r
     } else {
         step = mp_obj_get_int(self->step);
         if (step == 0) {
-            mp_raise_ValueError(MP_ERROR_TEXT("slice step cannot be zero"));
+            mp_raise_ValueError(MP_ERROR_TEXT("slice step can't be zero"));
         }
     }
 
diff --git a/py/objtype.c b/py/objtype.c
index 3f32cd6015..a8eeb1a9f7 100644
--- a/py/objtype.c
+++ b/py/objtype.c
@@ -989,9 +989,9 @@ STATIC mp_obj_t type_call(mp_obj_t self_in, size_t n_args, size_t n_kw, const mp
 
     if (self->make_new == NULL) {
         #if MICROPY_ERROR_REPORTING == MICROPY_ERROR_REPORTING_TERSE
-        mp_raise_TypeError(MP_ERROR_TEXT("cannot create instance"));
+        mp_raise_TypeError(MP_ERROR_TEXT("can't create instance"));
         #else
-        mp_raise_msg_varg(&mp_type_TypeError, MP_ERROR_TEXT("cannot create '%q' instances"), self->name);
+        mp_raise_msg_varg(&mp_type_TypeError, MP_ERROR_TEXT("can't create '%q' instances"), self->name);
         #endif
     }
 
diff --git a/py/runtime.c b/py/runtime.c
index cad2fc2563..1fa9e73f2a 100644
--- a/py/runtime.c
+++ b/py/runtime.c
@@ -1392,7 +1392,7 @@ mp_obj_t mp_import_from(mp_obj_t module, qstr name) {
     if (dest[1] != MP_OBJ_NULL) {
         // Hopefully we can't import bound method from an object
     import_error:
-        mp_raise_msg_varg(&mp_type_ImportError, MP_ERROR_TEXT("cannot import name %q"), name);
+        mp_raise_msg_varg(&mp_type_ImportError, MP_ERROR_TEXT("can't import name %q"), name);
     }
 
     if (dest[0] != MP_OBJ_NULL) {