diff --git a/tool b/tool
index 0aca649..8d68089 100755
--- a/tool
+++ b/tool
@@ -169,7 +169,7 @@ build_target() {
   local libraries=()
   local source_files=()
   local out_exe
-  add cc_flags -std=c99 -pipe -Wall -Wpedantic -Wextra -Wconversion -Werror=implicit-function-declaration -Werror=implicit-int -Werror=incompatible-pointer-types -Werror=int-conversion
+  add cc_flags -std=c99 -pipe -finput-charset=UTF-8 -Wall -Wpedantic -Wextra -Wconversion -Werror=implicit-function-declaration -Werror=implicit-int -Werror=incompatible-pointer-types -Werror=int-conversion
   if [[ $lld_detected = 1 ]]; then
     add cc_flags -fuse-ld=lld
   fi