1 files changed, 10 insertions, 2 deletions
diff --git a/soltools/mkdepend/collectdircontent.cxx b/soltools/mkdepend/collectdircontent.cxx
index c001ee05042c..3aa4981055fb 100644
--- a/soltools/mkdepend/collectdircontent.cxx
+++ b/soltools/mkdepend/collectdircontent.cxx
@@ -30,7 +30,11 @@ void IncludesCollection::add_to_collection(const string& dirPath) {
     }
     do {
         string winFileName(FindFileData.cFileName);
-        transform(winFileName.begin(), winFileName.end(), winFileName.begin(), rtl::toAsciiLowerCase);
+        transform(
+            winFileName.begin(), winFileName.end(), winFileName.begin(),
+            [](char c) {
+                return rtl::toAsciiLowerCase(static_cast<unsigned char>(c));
+            });
         dirContent.insert(winFileName);
     } while (FindNextFile(hFind, &FindFileData));
 #else
@@ -52,7 +56,11 @@ void IncludesCollection::add_to_collection(const string& dirPath) {
 
 bool IncludesCollection::exists(string filePath) {
 #if defined(_WIN32)
-    transform(filePath.begin(), filePath.end(), filePath.begin(), rtl::toAsciiLowerCase);
+    transform(
+        filePath.begin(), filePath.end(), filePath.begin(),
+        [](char c) {
+            return rtl::toAsciiLowerCase(static_cast<unsigned char>(c));
+        });
 #endif // defined( WNT )
     PathFilePair dirFile = split_path(filePath);
     string dirPath = dirFile.first;