diff --git a/cppsrc/U8x8lib.cpp b/cppsrc/U8x8lib.cpp
index ab1c81ca..e87abd93 100644
--- a/cppsrc/U8x8lib.cpp
+++ b/cppsrc/U8x8lib.cpp
@@ -713,7 +713,8 @@ extern "C" uint8_t u8x8_byte_arduino_hw_spi(u8x8_t *u8x8, uint8_t msg, uint8_t a
   
       break;
     case U8X8_MSG_BYTE_INIT:
-      u8x8->bus_clock = u8x8->display_info->sck_clock_hz;
+      if ( u8x8->bus_clock == 0 ) 	/* issue 769 */
+	u8x8->bus_clock = u8x8->display_info->sck_clock_hz;
       /* disable chipselect */
       u8x8_gpio_SetCS(u8x8, u8x8->display_info->chip_disable_level);
       
@@ -832,7 +833,8 @@ extern "C" uint8_t u8x8_byte_arduino_2nd_hw_spi(U8X8_UNUSED u8x8_t *u8x8, U8X8_U
   
       break;
     case U8X8_MSG_BYTE_INIT:
-      u8x8->bus_clock = u8x8->display_info->sck_clock_hz;
+      if ( u8x8->bus_clock == 0 ) 	/* issue 769 */
+	u8x8->bus_clock = u8x8->display_info->sck_clock_hz;
       /* disable chipselect */
       u8x8_gpio_SetCS(u8x8, u8x8->display_info->chip_disable_level);
       /* no wait required here */
@@ -1135,7 +1137,8 @@ extern "C" uint8_t u8x8_byte_arduino_hw_i2c(U8X8_UNUSED u8x8_t *u8x8, U8X8_UNUSE
       Wire.write((uint8_t *)arg_ptr, (int)arg_int);
       break;
     case U8X8_MSG_BYTE_INIT:
-      u8x8->bus_clock = u8x8->display_info->i2c_bus_clock_100kHz * 100000UL;
+      if ( u8x8->bus_clock == 0 ) 	/* issue 769 */
+	u8x8->bus_clock = u8x8->display_info->i2c_bus_clock_100kHz * 100000UL;
 #if defined(ESP8266) || defined(ARDUINO_ARCH_ESP8266) || defined(ESP_PLATFORM) || defined(ARDUINO_ARCH_ESP32)
       /* for ESP8266/ESP32, Wire.begin has two more arguments: clock and data */          
       if ( u8x8->pins[U8X8_PIN_I2C_CLOCK] != U8X8_PIN_NONE && u8x8->pins[U8X8_PIN_I2C_DATA] != U8X8_PIN_NONE )
@@ -1180,7 +1183,8 @@ extern "C" uint8_t u8x8_byte_arduino_2nd_hw_i2c(U8X8_UNUSED u8x8_t *u8x8, U8X8_U
       Wire1.write((uint8_t *)arg_ptr, (int)arg_int);
       break;
     case U8X8_MSG_BYTE_INIT:
-      u8x8->bus_clock = u8x8->display_info->i2c_bus_clock_100kHz * 100000UL;
+      if ( u8x8->bus_clock == 0 ) 	/* issue 769 */
+	u8x8->bus_clock = u8x8->display_info->i2c_bus_clock_100kHz * 100000UL;
       Wire1.begin();
       break;
     case U8X8_MSG_BYTE_SET_DC:
diff --git a/cppsrc/U8x8lib.h b/cppsrc/U8x8lib.h
index 2f48a978..e56b0d4f 100644
--- a/cppsrc/U8x8lib.h
+++ b/cppsrc/U8x8lib.h
@@ -111,6 +111,9 @@
 /* As of writing this, I did not found any official board which supports this */
 /* so this is not tested (May 2017), issue #224 */
 /* fixed ifdef, #410, #377 */
+/* meanwhile it is defined e.g. here: https://github.com/arduino/ArduinoCore-samd/blob/master/variants/mkrzero/variant.h#L91 */
+/* so it should be available for mkrzero */
+
 #ifdef SPI_INTERFACES_COUNT
 #if SPI_INTERFACES_COUNT > 1
 #define U8X8_HAVE_2ND_HW_SPI
diff --git a/csrc/u8x8_setup.c b/csrc/u8x8_setup.c
index f5b0d1b5..d931f119 100644
--- a/csrc/u8x8_setup.c
+++ b/csrc/u8x8_setup.c
@@ -102,6 +102,7 @@ void u8x8_SetupDefaults(u8x8_t *u8x8)
     u8x8->is_font_inverse_mode = 0;
     u8x8->device_address = 0;
     u8x8->utf8_state = 0;		/* also reset by u8x8_utf8_init */
+    u8x8->bus_clock = 0;		/* issue 769 */
     u8x8->i2c_address = 255;
     u8x8->debounce_default_pin_state = 255;	/* assume all low active buttons */