diff --git a/ports/stm32/machine_i2c.c b/ports/stm32/machine_i2c.c
index 5acf9c7d6e..2aebb9426e 100644
--- a/ports/stm32/machine_i2c.c
+++ b/ports/stm32/machine_i2c.c
@@ -48,26 +48,18 @@ typedef struct _machine_hard_i2c_obj_t {
     mp_hal_pin_obj_t sda;
 } machine_hard_i2c_obj_t;
 
-STATIC const machine_hard_i2c_obj_t machine_hard_i2c_obj[] = {
+STATIC const machine_hard_i2c_obj_t machine_hard_i2c_obj[MICROPY_HW_MAX_I2C] = {
     #if defined(MICROPY_HW_I2C1_SCL)
-    {{&machine_hard_i2c_type}, I2C1, MICROPY_HW_I2C1_SCL, MICROPY_HW_I2C1_SDA},
-    #else
-    {{NULL}, NULL, NULL, NULL},
+    [0] = {{&machine_hard_i2c_type}, I2C1, MICROPY_HW_I2C1_SCL, MICROPY_HW_I2C1_SDA},
     #endif
     #if defined(MICROPY_HW_I2C2_SCL)
-    {{&machine_hard_i2c_type}, I2C2, MICROPY_HW_I2C2_SCL, MICROPY_HW_I2C2_SDA},
-    #else
-    {{NULL}, NULL, NULL, NULL},
+    [1] = {{&machine_hard_i2c_type}, I2C2, MICROPY_HW_I2C2_SCL, MICROPY_HW_I2C2_SDA},
     #endif
     #if defined(MICROPY_HW_I2C3_SCL)
-    {{&machine_hard_i2c_type}, I2C3, MICROPY_HW_I2C3_SCL, MICROPY_HW_I2C3_SDA},
-    #else
-    {{NULL}, NULL, NULL, NULL},
+    [2] = {{&machine_hard_i2c_type}, I2C3, MICROPY_HW_I2C3_SCL, MICROPY_HW_I2C3_SDA},
     #endif
     #if defined(MICROPY_HW_I2C4_SCL)
-    {{&machine_hard_i2c_type}, I2C4, MICROPY_HW_I2C4_SCL, MICROPY_HW_I2C4_SDA},
-    #else
-    {{NULL}, NULL, NULL, NULL},
+    [3] = {{&machine_hard_i2c_type}, I2C4, MICROPY_HW_I2C4_SCL, MICROPY_HW_I2C4_SDA},
     #endif
 };
 
@@ -147,26 +139,18 @@ int machine_hard_i2c_transfer(mp_obj_base_t *self_in, uint16_t addr, size_t n, m
 
 typedef mp_machine_soft_i2c_obj_t machine_hard_i2c_obj_t;
 
-STATIC machine_hard_i2c_obj_t machine_hard_i2c_obj[] = {
+STATIC machine_hard_i2c_obj_t machine_hard_i2c_obj[MICROPY_HW_MAX_I2C] = {
     #if defined(MICROPY_HW_I2C1_SCL)
-    {{&machine_hard_i2c_type}, 1, I2C_POLL_DEFAULT_TIMEOUT_US, MICROPY_HW_I2C1_SCL, MICROPY_HW_I2C1_SDA},
-    #else
-    {{NULL}, 0, 0, NULL, NULL},
+    [0] = {{&machine_hard_i2c_type}, 1, I2C_POLL_DEFAULT_TIMEOUT_US, MICROPY_HW_I2C1_SCL, MICROPY_HW_I2C1_SDA},
     #endif
     #if defined(MICROPY_HW_I2C2_SCL)
-    {{&machine_hard_i2c_type}, 1, I2C_POLL_DEFAULT_TIMEOUT_US, MICROPY_HW_I2C2_SCL, MICROPY_HW_I2C2_SDA},
-    #else
-    {{NULL}, 0, 0, NULL, NULL},
+    [1] = {{&machine_hard_i2c_type}, 1, I2C_POLL_DEFAULT_TIMEOUT_US, MICROPY_HW_I2C2_SCL, MICROPY_HW_I2C2_SDA},
     #endif
     #if defined(MICROPY_HW_I2C3_SCL)
-    {{&machine_hard_i2c_type}, 1, I2C_POLL_DEFAULT_TIMEOUT_US, MICROPY_HW_I2C3_SCL, MICROPY_HW_I2C3_SDA},
-    #else
-    {{NULL}, 0, 0, NULL, NULL},
+    [2] = {{&machine_hard_i2c_type}, 1, I2C_POLL_DEFAULT_TIMEOUT_US, MICROPY_HW_I2C3_SCL, MICROPY_HW_I2C3_SDA},
     #endif
     #if defined(MICROPY_HW_I2C4_SCL)
-    {{&machine_hard_i2c_type}, 1, I2C_POLL_DEFAULT_TIMEOUT_US, MICROPY_HW_I2C4_SCL, MICROPY_HW_I2C4_SDA},
-    #else
-    {{NULL}, 0, 0, NULL, NULL},
+    [3] = {{&machine_hard_i2c_type}, 1, I2C_POLL_DEFAULT_TIMEOUT_US, MICROPY_HW_I2C4_SCL, MICROPY_HW_I2C4_SDA},
     #endif
 };
 
diff --git a/ports/stm32/mpconfigboard_common.h b/ports/stm32/mpconfigboard_common.h
index f3a3d48e7f..b9fa3833ec 100644
--- a/ports/stm32/mpconfigboard_common.h
+++ b/ports/stm32/mpconfigboard_common.h
@@ -180,6 +180,7 @@
 
 #define MP_HAL_UNIQUE_ID_ADDRESS (0x1ff1e800)
 #define PYB_EXTI_NUM_VECTORS (24)
+#define MICROPY_HW_MAX_I2C (4)
 #define MICROPY_HW_MAX_TIMER (17)
 #define MICROPY_HW_MAX_UART (8)
 
@@ -188,6 +189,7 @@
 
 #define MP_HAL_UNIQUE_ID_ADDRESS (0x1fff7590)
 #define PYB_EXTI_NUM_VECTORS (23)
+#define MICROPY_HW_MAX_I2C (4)
 #define MICROPY_HW_MAX_TIMER (17)
 #define MICROPY_HW_MAX_UART (6)