diff --git a/src/cairo-type1-subset.c b/src/cairo-type1-subset.c
index 2b07dfe8a..919b1d5c7 100644
--- a/src/cairo-type1-subset.c
+++ b/src/cairo-type1-subset.c
@@ -46,6 +46,8 @@
 #include FT_OUTLINE_H
 #include FT_TYPE1_TABLES_H
 
+#include <ctype.h>
+
 typedef struct _cairo_type1_font_subset {
 
     cairo_scaled_font_subset_t *scaled_font_subset;