diff --git a/micropython/bootloader/main.c b/micropython/bootloader/main.c
index da5c81204b..1faba54925 100644
--- a/micropython/bootloader/main.c
+++ b/micropython/bootloader/main.c
@@ -39,10 +39,10 @@ void display_vendor(const uint8_t *vimg, const char *vstr, uint32_t vstr_len, ui
     display_text_center(120, 192, vstr, vstr_len, FONT_BOLD, COLOR_WHITE, COLOR_BLACK);
     char ver_str[32];
     mini_snprintf(ver_str, sizeof(ver_str), "%d.%d.%d.%d",
-        fw_version & 0xFF,
-        (fw_version >> 8) & 0xFF,
-        (fw_version >> 16) & 0xFF,
-        (fw_version >> 24) & 0xFF
+        (int)(fw_version & 0xFF),
+        (int)((fw_version >> 8) & 0xFF),
+        (int)((fw_version >> 16) & 0xFF),
+        (int)((fw_version >> 24) & 0xFF)
     );
     display_text_center(120, 215, ver_str, -1, FONT_BOLD, COLOR_GRAY64, COLOR_BLACK);
     display_refresh();
diff --git a/micropython/extmod/modtrezorui/display.h b/micropython/extmod/modtrezorui/display.h
index 2803865abc..841ba598a2 100644
--- a/micropython/extmod/modtrezorui/display.h
+++ b/micropython/extmod/modtrezorui/display.h
@@ -54,7 +54,7 @@ void display_icon(int x, int y, int w, int h, const void *data, int datalen, uin
 #ifndef TREZOR_PRINT_DISABLE
 void display_print_color(uint16_t fgcolor, uint16_t bgcolor);
 void display_print(const char *text, int textlen);
-void display_printf(const char *fmt, ...);
+void display_printf(const char *fmt, ...) __attribute__ ((__format__ (__printf__, 1, 2)));
 #endif
 
 void display_text(int x, int y, const char *text, int textlen, uint8_t font, uint16_t fgcolor, uint16_t bgcolor);
diff --git a/micropython/trezorhal/mini_printf.h b/micropython/trezorhal/mini_printf.h
index 97e7c1170f..92f982ed13 100644
--- a/micropython/trezorhal/mini_printf.h
+++ b/micropython/trezorhal/mini_printf.h
@@ -37,8 +37,8 @@ extern "C" {
 
 #include <stdarg.h>
 
-int mini_vsnprintf(char* buffer, unsigned int buffer_len, const char *fmt, va_list va);
-int mini_snprintf(char* buffer, unsigned int buffer_len, const char *fmt, ...);
+int mini_vsnprintf(char* buffer, unsigned int buffer_len, const char *fmt, va_list va) __attribute__ ((__format__ (__printf__, 3, 0)));
+int mini_snprintf(char* buffer, unsigned int buffer_len, const char *fmt, ...) __attribute__ ((__format__ (__printf__, 3, 4)));
 
 #ifdef __cplusplus
 }
diff --git a/micropython/trezorhal/stm32_it.c b/micropython/trezorhal/stm32_it.c
index 22981dd919..e3e5218ed3 100644
--- a/micropython/trezorhal/stm32_it.c
+++ b/micropython/trezorhal/stm32_it.c
@@ -105,25 +105,25 @@ void HardFault_C_Handler(ExceptionRegisters_t *regs) {
 
     display_printf("HardFault\n");
 
-    display_printf("R0    %08x\n", regs->r0);
-    display_printf("R1    %08x\n", regs->r1);
-    display_printf("R2    %08x\n", regs->r2);
-    display_printf("R3    %08x\n", regs->r3);
-    display_printf("R12   %08x\n", regs->r12);
-    display_printf("SP    %08x\n", (uint32_t)regs);
-    display_printf("LR    %08x\n", regs->lr);
-    display_printf("PC    %08x\n", regs->pc);
-    display_printf("XPSR  %08x\n", regs->xpsr);
+    display_printf("R0    %08x\n", (unsigned int)regs->r0);
+    display_printf("R1    %08x\n", (unsigned int)regs->r1);
+    display_printf("R2    %08x\n", (unsigned int)regs->r2);
+    display_printf("R3    %08x\n", (unsigned int)regs->r3);
+    display_printf("R12   %08x\n", (unsigned int)regs->r12);
+    display_printf("SP    %08x\n", (unsigned int)regs);
+    display_printf("LR    %08x\n", (unsigned int)regs->lr);
+    display_printf("PC    %08x\n", (unsigned int)regs->pc);
+    display_printf("XPSR  %08x\n", (unsigned int)regs->xpsr);
 
     uint32_t cfsr = SCB->CFSR;
 
-    display_printf("HFSR  %08x\n", SCB->HFSR);
-    display_printf("CFSR  %08x\n", cfsr);
+    display_printf("HFSR  %08x\n", (unsigned int)SCB->HFSR);
+    display_printf("CFSR  %08x\n", (unsigned int)cfsr);
     if (cfsr & 0x80) {
-        display_printf("MMFAR %08x\n", SCB->MMFAR);
+        display_printf("MMFAR %08x\n", (unsigned int)SCB->MMFAR);
     }
     if (cfsr & 0x8000) {
-        display_printf("BFAR  %08x\n", SCB->BFAR);
+        display_printf("BFAR  %08x\n", (unsigned int)SCB->BFAR);
     }
 
     if ((void*)&_ram_start <= (void*)regs && (void*)regs < (void*)&_ram_end) {
@@ -134,7 +134,7 @@ void HardFault_C_Handler(ExceptionRegisters_t *regs) {
             stack_top = (uint32_t*)regs + 32;
         }
         for (uint32_t *sp = (uint32_t*)regs; sp < stack_top; ++sp) {
-            display_printf("  %08x  %08x\n", (uint32_t)sp, *sp);
+            display_printf("  %08x  %08x\n", (unsigned int)sp, (unsigned int)*sp);
         }
     }