--- a/src/java.instrument/share/native/libinstrument/JarFacade.c
+++ b/src/java.instrument/share/native/libinstrument/JarFacade.c
@@ -23,6 +23,7 @@
  * questions.
  */
 
+#include <ctype.h>
 #include <string.h>
 #include <stdlib.h>