diff --git a/embed/extmod/modtrezorui/display-stm32.h b/embed/extmod/modtrezorui/display-stm32.h
index 87bb566d..52419d20 100644
--- a/embed/extmod/modtrezorui/display-stm32.h
+++ b/embed/extmod/modtrezorui/display-stm32.h
@@ -271,6 +271,6 @@ void display_refresh(void)
     while (GPIO_PIN_SET == HAL_GPIO_ReadPin(GPIOD, GPIO_PIN_12)) { }
 }
 
-void display_save(const char *filename)
+void display_save(const char *prefix)
 {
 }
diff --git a/embed/extmod/modtrezorui/display-unix.h b/embed/extmod/modtrezorui/display-unix.h
index 796589ce..0ada6de2 100644
--- a/embed/extmod/modtrezorui/display-unix.h
+++ b/embed/extmod/modtrezorui/display-unix.h
@@ -153,12 +153,16 @@ static void display_set_backlight(int val)
     display_refresh();
 }
 
-void display_save(const char *filename)
+void display_save(const char *prefix)
 {
 #ifndef TREZOR_NOUI
     if (!RENDERER) {
         display_init();
     }
-    IMG_SavePNG(BUFFER, filename);
+    static uint32_t cnt = 0;
+    char fname[256];
+    snprintf(fname, sizeof(fname), "%s%08d.png", prefix, cnt);
+    IMG_SavePNG(BUFFER, fname);
+    cnt++;
 #endif
 }
diff --git a/embed/extmod/modtrezorui/display.h b/embed/extmod/modtrezorui/display.h
index 752a5faa..ea9befdb 100644
--- a/embed/extmod/modtrezorui/display.h
+++ b/embed/extmod/modtrezorui/display.h
@@ -54,7 +54,7 @@
 
 void display_init(void);
 void display_refresh(void);
-void display_save(const char *filename);
+void display_save(const char *prefix);
 
 // provided by common
 
diff --git a/embed/extmod/modtrezorui/modtrezorui-display.h b/embed/extmod/modtrezorui/modtrezorui-display.h
index c6f90d8e..5e2f4849 100644
--- a/embed/extmod/modtrezorui/modtrezorui-display.h
+++ b/embed/extmod/modtrezorui/modtrezorui-display.h
@@ -414,15 +414,15 @@ STATIC mp_obj_t mod_trezorui_Display_offset(size_t n_args, const mp_obj_t *args)
 }
 STATIC MP_DEFINE_CONST_FUN_OBJ_VAR_BETWEEN(mod_trezorui_Display_offset_obj, 1, 2, mod_trezorui_Display_offset);
 
-/// def save(self, filename: str) -> None:
+/// def save(self, prefix: str) -> None:
 ///     '''
-///     Saves current display contents to file filename.
+///     Saves current display contents to PNG file with given prefix.
 ///     '''
-STATIC mp_obj_t mod_trezorui_Display_save(mp_obj_t self, mp_obj_t filename) {
-    mp_buffer_info_t fn;
-    mp_get_buffer_raise(filename, &fn, MP_BUFFER_READ);
-    if (fn.len > 0) {
-        display_save(fn.buf);
+STATIC mp_obj_t mod_trezorui_Display_save(mp_obj_t self, mp_obj_t prefix) {
+    mp_buffer_info_t pfx;
+    mp_get_buffer_raise(prefix, &pfx, MP_BUFFER_READ);
+    if (pfx.len > 0) {
+        display_save(pfx.buf);
     }
     return mp_const_none;
 }