diff --git a/c/qrcodegen.c b/c/qrcodegen.c
index 8168063..7b5bba6 100644
--- a/c/qrcodegen.c
+++ b/c/qrcodegen.c
@@ -460,7 +460,8 @@ testable uint8_t finiteFieldMultiply(uint8_t x, uint8_t y) {
 static void initializeFunctionModules(int version, uint8_t qrcode[]) {
 	// Initialize QR Code
 	int qrsize = qrcodegen_getSize(version);
-	memset(qrcode, 0, (qrsize * qrsize + 7) / 8 * sizeof(qrcode[0]));
+	memset(qrcode, 0, ((qrsize * qrsize + 7) / 8 + 1) * sizeof(qrcode[0]));
+	qrcode[0] = (uint8_t)qrsize;
 	
 	// Fill horizontal and vertical timing patterns
 	fillRectangle(6, 0, 1, qrsize, qrcode, qrsize);
@@ -785,7 +786,7 @@ static bool getModule(const uint8_t qrcode[], int qrsize, int x, int y) {
 	assert(21 <= qrsize && qrsize <= 177 && 0 <= x && x < qrsize && 0 <= y && y < qrsize);
 	int index = y * qrsize + x;
 	int bitIndex = index & 7;
-	int byteIndex = index >> 3;
+	int byteIndex = (index >> 3) + 1;
 	return ((qrcode[byteIndex] >> bitIndex) & 1) != 0;
 }
 
@@ -795,7 +796,7 @@ static void setModule(uint8_t qrcode[], int qrsize, int x, int y, bool isBlack)
 	assert(21 <= qrsize && qrsize <= 177 && 0 <= x && x < qrsize && 0 <= y && y < qrsize);
 	int index = y * qrsize + x;
 	int bitIndex = index & 7;
-	int byteIndex = index >> 3;
+	int byteIndex = (index >> 3) + 1;
 	if (isBlack)
 		qrcode[byteIndex] |= 1 << bitIndex;
 	else
diff --git a/c/qrcodegen.h b/c/qrcodegen.h
index f53e696..c56c292 100644
--- a/c/qrcodegen.h
+++ b/c/qrcodegen.h
@@ -66,7 +66,7 @@ enum qrcodegen_Mask {
 // Calculates the number of bytes needed to store any QR Code up to and including the given version number,
 // as a compile-time constant. For example, 'uint8_t buffer[qrcodegen_BUFFER_LEN_FOR_VERSION(25)];'
 // can store any single QR Code from version 1 to 25, inclusive.
-#define qrcodegen_BUFFER_LEN_FOR_VERSION(n)  ((((n) * 4 + 17) * ((n) * 4 + 17) + 7) / 8)
+#define qrcodegen_BUFFER_LEN_FOR_VERSION(n)  ((((n) * 4 + 17) * ((n) * 4 + 17) + 7) / 8 + 1)
 
 // The worst-case number of bytes needed to store one QR Code, up to and including
 // version 40. This value equals 3917, which is just under 4 kilobytes.
@@ -105,7 +105,7 @@ int qrcodegen_encodeBinary(uint8_t dataAndTemp[], size_t dataLen, uint8_t qrcode
  * Returns the side length of any QR Code of the given version number.
  * The version must be in the range [1, 40]. The result is in the range [21, 177].
  * Note that every 'uint8_t qrcode[]' buffer must have a length of at least
- * ceil(size^2 / 8), which also equals qrcodegen_BUFFER_LEN_FOR_VERSION(version).
+ * ceil(size^2 / 8 + 1), which also equals qrcodegen_BUFFER_LEN_FOR_VERSION(version).
  */
 int qrcodegen_getSize(int version);