1 files changed, 5 insertions, 2 deletions
diff --git a/native/jni/src/char_utils.h b/native/jni/src/char_utils.h
index 607dc5195..21dca9a0a 100644
--- a/native/jni/src/char_utils.h
+++ b/native/jni/src/char_utils.h
@@ -50,8 +50,7 @@ inline static unsigned short toBaseChar(unsigned short c) {
     return c;
 }
 
-inline static unsigned short toBaseLowerCase(unsigned short c) {
-    c = toBaseChar(c);
+inline static unsigned short toLowerCase(const unsigned short c) {
     if (isAsciiUpper(c)) {
         return toAsciiLower(c);
     } else if (isAscii(c)) {
@@ -60,6 +59,10 @@ inline static unsigned short toBaseLowerCase(unsigned short c) {
     return latin_tolower(c);
 }
 
+inline static unsigned short toBaseLowerCase(const unsigned short c) {
+    return toLowerCase(toBaseChar(c));
+}
+
 } // namespace latinime
 
 #endif // LATINIME_CHAR_UTILS_H