diff --git a/Utilities/cmtar/CMakeLists.txt b/Utilities/cmtar/CMakeLists.txt
index 80137ca33d..328a9009e6 100644
--- a/Utilities/cmtar/CMakeLists.txt
+++ b/Utilities/cmtar/CMakeLists.txt
@@ -212,7 +212,7 @@ ELSE(HAVE_SIZEOF_UID_T)
 ENDIF(HAVE_SIZEOF_UID_T)
 
 #SET (HAVE_BASENAME 0)
-#SET (HAVE_CTYPE_H 0)
+SET (HAVE_CTYPE_H 1) # all our platforms have <ctype.h>
 #SET (HAVE_DEV_T 1)
 #SET (HAVE_DIRNAME 0)
 #SET (HAVE_FNMATCH 1)