1 files changed, 1 insertions, 0 deletions
diff --git a/stc/cstr.h b/stc/cstr.h
index a083c807..3ec55451 100644
--- a/stc/cstr.h
+++ b/stc/cstr.h
@@ -28,6 +28,7 @@
 #include <string.h>
 #include <stdarg.h>
 #include <stdio.h> /* vsnprintf */
+#include <ctype.h>
 
 typedef struct cstr { char* str; } cstr_t;
 typedef struct { char *val; } cstr_iter_t;