diff --git a/extmod/utime_mphal.c b/extmod/utime_mphal.c
index e99ba46ce5..0fe3a3ba1d 100644
--- a/extmod/utime_mphal.c
+++ b/extmod/utime_mphal.c
@@ -38,7 +38,7 @@
 
 STATIC mp_obj_t time_sleep(mp_obj_t seconds_o) {
     #if MICROPY_PY_BUILTINS_FLOAT
-    mp_hal_delay_ms(1000 * mp_obj_get_float(seconds_o));
+    mp_hal_delay_ms((mp_uint_t)(1000 * mp_obj_get_float(seconds_o)));
     #else
     mp_hal_delay_ms(1000 * mp_obj_get_int(seconds_o));
     #endif
diff --git a/py/builtinimport.c b/py/builtinimport.c
index 7746e26a4b..7a8474cac3 100644
--- a/py/builtinimport.c
+++ b/py/builtinimport.c
@@ -227,10 +227,11 @@ STATIC void do_load(mp_obj_t module_obj, vstr_t *file) {
         do_load_from_lexer(module_obj, lex);
         return;
     }
-    #endif
+    #else
 
     // If we get here then the file was not frozen and we can't compile scripts.
     mp_raise_msg(&mp_type_ImportError, "script compilation not supported");
+    #endif
 }
 
 STATIC void chop_component(const char *start, const char **end) {
diff --git a/py/emitbc.c b/py/emitbc.c
index ec12a62c6c..127bf0bf9a 100644
--- a/py/emitbc.c
+++ b/py/emitbc.c
@@ -902,7 +902,7 @@ void mp_emit_bc_make_closure(emit_t *emit, scope_t *scope, mp_uint_t n_closed_ov
         emit_write_bytecode_byte(emit, n_closed_over);
     } else {
         assert(n_closed_over <= 255);
-        emit_bc_pre(emit, -2 - n_closed_over + 1);
+        emit_bc_pre(emit, -2 - (mp_int_t)n_closed_over + 1);
         emit_write_bytecode_byte_raw_code(emit, MP_BC_MAKE_CLOSURE_DEFARGS, scope->raw_code);
         emit_write_bytecode_byte(emit, n_closed_over);
     }
diff --git a/py/formatfloat.c b/py/formatfloat.c
index b16746b39b..ea5a07977b 100644
--- a/py/formatfloat.c
+++ b/py/formatfloat.c
@@ -332,7 +332,7 @@ int mp_format_float(FPTYPE f, char *buf, size_t buf_size, char fmt, int prec, ch
 
     // Print the digits of the mantissa
     for (int i = 0; i < num_digits; ++i, --dec) {
-        int32_t d = f;
+        int32_t d = (int32_t)f;
         *s++ = '0' + d;
         if (dec == 0 && prec > 0) {
             *s++ = '.';
diff --git a/py/lexer.c b/py/lexer.c
index abc1f3ebbb..6e5cc18f44 100644
--- a/py/lexer.c
+++ b/py/lexer.c
@@ -672,7 +672,7 @@ mp_lexer_t *mp_lexer_new(qstr src_name, mp_reader_t reader) {
     lex->source_name = src_name;
     lex->reader = reader;
     lex->line = 1;
-    lex->column = -2;   // account for 3 dummy bytes
+    lex->column = (size_t)-2; // account for 3 dummy bytes
     lex->emit_dent = 0;
     lex->nested_bracket_level = 0;
     lex->alloc_indent_level = MICROPY_ALLOC_LEXER_INDENT_INIT;
diff --git a/py/modbuiltins.c b/py/modbuiltins.c
index 57d471b1fc..8fbf4daeb2 100644
--- a/py/modbuiltins.c
+++ b/py/modbuiltins.c
@@ -91,10 +91,8 @@ STATIC mp_obj_t mp_builtin___build_class__(size_t n_args, const mp_obj_t *args)
 MP_DEFINE_CONST_FUN_OBJ_VAR(mp_builtin___build_class___obj, 2, mp_builtin___build_class__);
 
 STATIC mp_obj_t mp_builtin_abs(mp_obj_t o_in) {
-    if (0) {
-        // dummy
-#if MICROPY_PY_BUILTINS_FLOAT
-    } else if (mp_obj_is_float(o_in)) {
+    #if MICROPY_PY_BUILTINS_FLOAT
+    if (mp_obj_is_float(o_in)) {
         mp_float_t value = mp_obj_float_get(o_in);
         // TODO check for NaN etc
         if (value < 0) {
@@ -102,17 +100,17 @@ STATIC mp_obj_t mp_builtin_abs(mp_obj_t o_in) {
         } else {
             return o_in;
         }
-#if MICROPY_PY_BUILTINS_COMPLEX
+    #if MICROPY_PY_BUILTINS_COMPLEX
     } else if (MP_OBJ_IS_TYPE(o_in, &mp_type_complex)) {
         mp_float_t real, imag;
         mp_obj_complex_get(o_in, &real, &imag);
         return mp_obj_new_float(MICROPY_FLOAT_C_FUN(sqrt)(real*real + imag*imag));
-#endif
-#endif
-    } else {
-        // this will raise a TypeError if the argument is not integral
-        return mp_obj_int_abs(o_in);
+    #endif
     }
+    #endif
+
+    // this will raise a TypeError if the argument is not integral
+    return mp_obj_int_abs(o_in);
 }
 MP_DEFINE_CONST_FUN_OBJ_1(mp_builtin_abs_obj, mp_builtin_abs);
 
diff --git a/py/objint.c b/py/objint.c
index 0b49041399..2749ec51c2 100644
--- a/py/objint.c
+++ b/py/objint.c
@@ -106,7 +106,7 @@ STATIC mp_fp_as_int_class_t mp_classify_fp_as_int(mp_float_t val) {
 #define MP_FLOAT_SIGN_SHIFT_I32 ((MP_FLOAT_FRAC_BITS + MP_FLOAT_EXP_BITS) % 32)
 #define MP_FLOAT_EXP_SHIFT_I32 (MP_FLOAT_FRAC_BITS % 32)
 
-    if (e & (1 << MP_FLOAT_SIGN_SHIFT_I32)) {
+    if (e & (1U << MP_FLOAT_SIGN_SHIFT_I32)) {
 #if MICROPY_FLOAT_IMPL == MICROPY_FLOAT_IMPL_DOUBLE
         e |= u.i[MP_ENDIANNESS_BIG] != 0;
 #endif
diff --git a/py/runtime.c b/py/runtime.c
index 0a3a4b12dc..a8a1f73fa4 100644
--- a/py/runtime.c
+++ b/py/runtime.c
@@ -1410,16 +1410,13 @@ mp_obj_t mp_parse_compile_execute(mp_lexer_t *lex, mp_parse_input_kind_t parse_i
 
 NORETURN void *m_malloc_fail(size_t num_bytes) {
     DEBUG_printf("memory allocation failed, allocating %u bytes\n", (uint)num_bytes);
-    if (0) {
-        // dummy
     #if MICROPY_ENABLE_GC
-    } else if (gc_is_locked()) {
+    if (gc_is_locked()) {
         mp_raise_msg(&mp_type_MemoryError, "memory allocation failed, heap is locked");
-    #endif
-    } else {
-        nlr_raise(mp_obj_new_exception_msg_varg(&mp_type_MemoryError,
-            "memory allocation failed, allocating %u bytes", (uint)num_bytes));
     }
+    #endif
+    nlr_raise(mp_obj_new_exception_msg_varg(&mp_type_MemoryError,
+        "memory allocation failed, allocating %u bytes", (uint)num_bytes));
 }
 
 NORETURN void mp_raise_msg(const mp_obj_type_t *exc_type, const char *msg) {
diff --git a/py/vstr.c b/py/vstr.c
index 6a91552b5a..f41bd2e232 100644
--- a/py/vstr.c
+++ b/py/vstr.c
@@ -34,7 +34,7 @@
 #include "py/mpprint.h"
 
 // returned value is always at least 1 greater than argument
-#define ROUND_ALLOC(a) (((a) & ((~0) - 7)) + 8)
+#define ROUND_ALLOC(a) (((a) & ((~0U) - 7)) + 8)
 
 // Init the vstr so it allocs exactly given number of bytes.  Set length to zero.
 void vstr_init(vstr_t *vstr, size_t alloc) {