diff --git a/src/kiwano/platform/FileSystem.cpp b/src/kiwano/platform/FileSystem.cpp
index d3091581..4cbeb675 100644
--- a/src/kiwano/platform/FileSystem.cpp
+++ b/src/kiwano/platform/FileSystem.cpp
@@ -18,6 +18,7 @@
 // OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
 // THE SOFTWARE.
 
+#include <cctype>
 #include <kiwano/platform/FileSystem.h>
 
 namespace kiwano