diff --git a/ports/unix/Makefile b/ports/unix/Makefile
index 32e3b44b227..def45e2a405 100644
--- a/ports/unix/Makefile
+++ b/ports/unix/Makefile
@@ -49,9 +49,10 @@ INC += -I$(BUILD)
 
 # compiler settings
 CWARN = -Wall -Werror
-// CIRCUITPY-CHANGE: add  -Wno-missing-field-initializers
+# CIRCUITPY-CHANGE: add  -Wno-missing-field-initializers
 CWARN += -Wextra -Wno-unused-parameter -Wpointer-arith -Wdouble-promotion -Wfloat-conversion -Wno-missing-field-initializers
-CFLAGS += $(INC) $(CWARN) -std=gnu99 -DUNIX $(COPT) -I$(VARIANT_DIR) $(CFLAGS_EXTRA)
+# CIRCUITPY-CHANGE: use gnu11 instead of gnu99
+CFLAGS += $(INC) $(CWARN) -std=gnu11 -DUNIX $(COPT) -I$(VARIANT_DIR) $(CFLAGS_EXTRA)
 
 # Force the use of 64-bits for file sizes in C library functions on 32-bit platforms.
 # This option has no effect on 64-bit builds.
@@ -262,7 +263,8 @@ CFLAGS += -DMPZ_DIG_SIZE=16 # force 16 bits to work on both 32 and 64 bit archs
 CFLAGS += -DMICROPY_MODULE_FROZEN_STR
 endif
 
-CXXFLAGS += $(filter-out -Wmissing-prototypes -Wold-style-definition -std=gnu99,$(CFLAGS) $(CXXFLAGS_MOD))
+# CIRCUITPY-CHANGE: use gnu11 instead of gnu99
+CXXFLAGS += $(filter-out -Wmissing-prototypes -Wold-style-definition -std=gnu11,$(CFLAGS) $(CXXFLAGS_MOD))
 
 ifeq ($(MICROPY_FORCE_32BIT),1)
 RUN_TESTS_MPY_CROSS_FLAGS = --mpy-cross-flags='-march=x86'
diff --git a/ports/unix/variants/coverage/mpconfigvariant.mk b/ports/unix/variants/coverage/mpconfigvariant.mk
index 0dd93b25cf4..2ef5b0a1bdb 100644
--- a/ports/unix/variants/coverage/mpconfigvariant.mk
+++ b/ports/unix/variants/coverage/mpconfigvariant.mk
@@ -150,6 +150,10 @@ SRC_C += $(addprefix lib/mp3/src/, \
 
 $(BUILD)/lib/mp3/src/buffers.o: CFLAGS += -include "shared-module/audiomp3/__init__.h" -D'MPDEC_ALLOCATOR(x)=malloc(x)' -D'MPDEC_FREE(x)=free(x)' -fwrapv
 
+# mp3dec.h only recognizes a fixed list of platforms and errors out on anything
+# else, including aarch64. Ask for the portable C code path, like espressif does.
+CFLAGS += -DMP3DEC_GENERIC
+
 CFLAGS += \
 	-DCIRCUITPY_AESIO=1 \
 	-DCIRCUITPY_AUDIOCORE=1 \
diff --git a/shared-bindings/audiomp3/MP3Decoder.h b/shared-bindings/audiomp3/MP3Decoder.h
index 0b485b4bca1..e316b061248 100644
--- a/shared-bindings/audiomp3/MP3Decoder.h
+++ b/shared-bindings/audiomp3/MP3Decoder.h
@@ -19,5 +19,5 @@ void common_hal_audiomp3_mp3file_construct(audiomp3_mp3file_obj_t *self,
 
 void common_hal_audiomp3_mp3file_set_file(audiomp3_mp3file_obj_t *self, mp_obj_t stream);
 void common_hal_audiomp3_mp3file_deinit(audiomp3_mp3file_obj_t *self);
-float common_hal_audiomp3_mp3file_get_rms_level(audiomp3_mp3file_obj_t *self);
+mp_float_t common_hal_audiomp3_mp3file_get_rms_level(audiomp3_mp3file_obj_t *self);
 uint32_t common_hal_audiomp3_mp3file_get_samples_decoded(audiomp3_mp3file_obj_t *self);
diff --git a/shared-module/audiomp3/MP3Decoder.c b/shared-module/audiomp3/MP3Decoder.c
index 6f0b5d4723f..463fccf9708 100644
--- a/shared-module/audiomp3/MP3Decoder.c
+++ b/shared-module/audiomp3/MP3Decoder.c
@@ -517,14 +517,14 @@ audioio_get_buffer_result_t audiomp3_mp3file_get_buffer(audiomp3_mp3file_obj_t *
     return result;
 }
 
-float common_hal_audiomp3_mp3file_get_rms_level(audiomp3_mp3file_obj_t *self) {
-    float sumsq = 0.f;
+mp_float_t common_hal_audiomp3_mp3file_get_rms_level(audiomp3_mp3file_obj_t *self) {
+    mp_float_t sumsq = MICROPY_FLOAT_CONST(0.0);
     // Assumes no DC component to the audio.  Is that a safe assumption?
     int16_t *buffer = (int16_t *)(void *)self->pcm_buffer[self->buffer_index];
     for (size_t i = 0; i < self->base.max_buffer_length / sizeof(int16_t); i++) {
-        sumsq += (float)buffer[i] * buffer[i];
+        sumsq += (mp_float_t)buffer[i] * buffer[i];
     }
-    return sqrtf(sumsq) / (self->base.max_buffer_length / sizeof(int16_t));
+    return MICROPY_FLOAT_C_FUN(sqrt)(sumsq) / (self->base.max_buffer_length / sizeof(int16_t));
 }
 
 uint32_t common_hal_audiomp3_mp3file_get_samples_decoded(audiomp3_mp3file_obj_t *self) {