diff --git a/render.c b/render.c
index 91431c71..adc6fb9e 100644
--- a/render.c
+++ b/render.c
@@ -2,7 +2,6 @@
 
 #include <string.h>
 #include <wctype.h>
-#include <ctype.h>
 #include <unistd.h>
 #include <signal.h>
 
@@ -573,7 +572,7 @@ render_cell(struct terminal *term, pixman_image_t *pix, pixman_region32_t *damag
                  * NOTE: if changing this, also update render_margin()
                  */
                 xassert(alpha == 0xffff);
-            } else if (isspace(cell->wc) || cell->wc == 0) {
+            } else if (isc32space(cell->wc) || cell->wc == 0) {
                 alpha = term->colors.alpha;
             } else {
                 alpha = term->colors.alpha_non_whitespace;