diff --git a/mlpp/data/data.cpp b/mlpp/data/data.cpp
index 2ccac6e..efc330e 100644
--- a/mlpp/data/data.cpp
+++ b/mlpp/data/data.cpp
@@ -1086,10 +1086,12 @@ MLPPData::WordsToVecResult MLPPData::word_to_vec(std::vector<std::string> senten
 	for (uint32_t i = 0; i < segmented_sentences.size(); i++) {
 		for (uint32_t j = 0; j < segmented_sentences[i].size(); j++) {
 			for (int k = windowSize; k > 0; k--) {
-				if (j - k >= 0) {
+				int jmk = (int)j - k;
+
+				if (jmk >= 0) {
 					inputStrings.push_back(segmented_sentences[i][j]);
 
-					outputStrings.push_back(segmented_sentences[i][j - k]);
+					outputStrings.push_back(segmented_sentences[i][jmk]);
 				}
 				if (j + k <= segmented_sentences[i].size() - 1) {
 					inputStrings.push_back(segmented_sentences[i][j]);
diff --git a/mlpp/data/data_old.cpp b/mlpp/data/data_old.cpp
index 2fec574..488fc13 100644
--- a/mlpp/data/data_old.cpp
+++ b/mlpp/data/data_old.cpp
@@ -597,10 +597,12 @@ std::tuple<std::vector<std::vector<real_t>>, std::vector<std::string>> MLPPDataO
 	for (uint32_t i = 0; i < segmented_sentences.size(); i++) {
 		for (uint32_t j = 0; j < segmented_sentences[i].size(); j++) {
 			for (int k = windowSize; k > 0; k--) {
-				if (j - k >= 0) {
+				int jmk = (int)j - k;
+
+				if (jmk >= 0) {
 					inputStrings.push_back(segmented_sentences[i][j]);
 
-					outputStrings.push_back(segmented_sentences[i][j - k]);
+					outputStrings.push_back(segmented_sentences[i][jmk]);
 				}
 				if (j + k <= segmented_sentences[i].size() - 1) {
 					inputStrings.push_back(segmented_sentences[i][j]);