diff --git a/lib/rtc_ds1307.c b/lib/rtc_ds1307.c
index 5724eb3..d5f2f61 100644
--- a/lib/rtc_ds1307.c
+++ b/lib/rtc_ds1307.c
@@ -199,7 +199,7 @@ bool rtc_ds1307_read_ram(uint8_t start, uint8_t* data, uint8_t length)
 	}
 
 	const uint8_t address[] = {0x08+start}; // memory address for data
-	return i2c_master_read(RTC_DS1307_I2C_ADDR, address, LENGTH(address), data, LENGTH(data)); // read RAM (starting at 0x08)
+	return i2c_master_read(RTC_DS1307_I2C_ADDR, address, LENGTH(address), data, length); // read RAM (starting at 0x08)
 }
 
 bool rtc_ds1307_read_rom(uint16_t start, uint8_t* data, uint16_t length)
@@ -213,7 +213,7 @@ bool rtc_ds1307_read_rom(uint16_t start, uint8_t* data, uint16_t length)
 	}
 
 	const uint8_t address[] = {start>>8, start}; // memory address for data
-	return i2c_master_read(RTC_DS1307_EEPROM_ADDR, address, LENGTH(address), data, LENGTH(data)); // read ROM
+	return i2c_master_read(RTC_DS1307_EEPROM_ADDR, address, LENGTH(address), data, length); // read ROM
 }
 
 bool rtc_ds1307_oscillator_disable(void)
@@ -409,7 +409,7 @@ bool rtc_ds1307_write_ram(uint8_t start, uint8_t* data, uint8_t length)
 		return false;
 	}
 	const uint8_t address[] = {0x08+start}; // memory address for data
-	return i2c_master_write(RTC_DS1307_I2C_ADDR, address, LENGTH(address), data, LENGTH(data)); // write RAM (starting at 0x08)
+	return i2c_master_write(RTC_DS1307_I2C_ADDR, address, LENGTH(address), data, length); // write RAM (starting at 0x08)
 }
 
 bool rtc_ds1307_write_rom(uint16_t start, uint8_t* data, uint8_t length)
@@ -425,5 +425,5 @@ bool rtc_ds1307_write_rom(uint16_t start, uint8_t* data, uint8_t length)
 		return false;
 	}
 	const uint8_t address[] = {start>>8, start}; // memory address for data
-	return i2c_master_write(RTC_DS1307_EEPROM_ADDR, address, LENGTH(address), data, LENGTH(data)); // write ROM
+	return i2c_master_write(RTC_DS1307_EEPROM_ADDR, address, LENGTH(address), data, length); // write ROM
 }