diff --git a/cpp/QrCode.cpp b/cpp/QrCode.cpp
index c849f44..9eef0e4 100644
--- a/cpp/QrCode.cpp
+++ b/cpp/QrCode.cpp
@@ -104,7 +104,7 @@ QrCode QrCode::encodeSegments(const vector<QrSegment> &segs, Ecc ecl,
 		throw std::logic_error("Assertion error");
 	
 	// Add terminator and pad up to a byte if applicable
-	size_t dataCapacityBits = getNumDataCodewords(version, ecl) * 8;
+	size_t dataCapacityBits = static_cast<size_t>(getNumDataCodewords(version, ecl)) * 8;
 	if (bb.size() > dataCapacityBits)
 		throw std::logic_error("Assertion error");
 	bb.appendBits(0, std::min(4, static_cast<int>(dataCapacityBits - bb.size())));
@@ -235,7 +235,7 @@ void QrCode::drawFunctionPatterns() {
 	
 	// Draw numerous alignment patterns
 	const vector<int> alignPatPos = getAlignmentPatternPositions();
-	int numAlign = alignPatPos.size();
+	int numAlign = static_cast<int>(alignPatPos.size());
 	for (int i = 0; i < numAlign; i++) {
 		for (int j = 0; j < numAlign; j++) {
 			// Don't draw on the three finder corners
@@ -348,7 +348,7 @@ vector<uint8_t> QrCode::addEccAndInterleave(const vector<uint8_t> &data) const {
 	const vector<uint8_t> rsDiv = reedSolomonComputeDivisor(blockEccLen);
 	for (int i = 0, k = 0; i < numBlocks; i++) {
 		vector<uint8_t> dat(data.cbegin() + k, data.cbegin() + (k + shortBlockLen - blockEccLen + (i < numShortBlocks ? 0 : 1)));
-		k += dat.size();
+		k += static_cast<int>(dat.size());
 		const vector<uint8_t> ecc = reedSolomonComputeRemainder(dat, rsDiv);
 		if (i < numShortBlocks)
 			dat.push_back(0);
diff --git a/cpp/QrCodeGeneratorWorker.cpp b/cpp/QrCodeGeneratorWorker.cpp
index 2295593..073107f 100644
--- a/cpp/QrCodeGeneratorWorker.cpp
+++ b/cpp/QrCodeGeneratorWorker.cpp
@@ -26,6 +26,7 @@
  *   Software.
  */
 
+#include <cstddef>
 #include <cstdint>
 #include <cstdlib>
 #include <cstring>
@@ -83,7 +84,7 @@ int main() {
 		
 		try {  // Try to make QR Code symbol
 			const QrCode qr = QrCode::encodeSegments(segs,
-				ECC_LEVELS.at(errCorLvl), minVersion, maxVersion, mask, boostEcl == 1);
+				ECC_LEVELS.at(static_cast<std::size_t>(errCorLvl)), minVersion, maxVersion, mask, boostEcl == 1);
 			// Print grid of modules
 			std::cout << qr.getVersion() << std::endl;
 			for (int y = 0; y < qr.getSize(); y++) {