diff --git a/libfuse-lite/fuse_opt.c b/libfuse-lite/fuse_opt.c
index 1c6a3157..13a27a63 100644
--- a/libfuse-lite/fuse_opt.c
+++ b/libfuse-lite/fuse_opt.c
@@ -200,7 +200,7 @@ static int process_opt(struct fuse_opt_context *ctx,
         if (call_proc(ctx, arg, opt->value, iso) == -1)
             return -1;
     } else {
-        void *var = ctx->data + opt->offset;
+        void *var = (char *)ctx->data + opt->offset;
         if (sep && opt->templ[sep + 1]) {
             const char *param = arg + sep;
             if (opt->templ[sep] == '=')