diff --git a/ares_build.h.dist b/ares_build.h.dist
index 9f32c8f2..d88a65cd 100644
--- a/ares_build.h.dist
+++ b/ares_build.h.dist
@@ -174,26 +174,26 @@
 #  if defined(__IBMC__) || defined(__IBMCPP__)
 #    if defined(_ILP32)
 #      define CARES_SIZEOF_LONG           4
-#      define CARES_TYPEOF_ARES_SOCKLEN_T FIXME
-#      define CARES_SIZEOF_ARES_SOCKLEN_T -1
 #    elif defined(_LP64)
 #      define CARES_SIZEOF_LONG           8
-#      define CARES_TYPEOF_ARES_SOCKLEN_T FIXME
-#      define CARES_SIZEOF_ARES_SOCKLEN_T -1
 #    endif
+#    define CARES_TYPEOF_ARES_SOCKLEN_T socklen_t
+#    define CARES_SIZEOF_ARES_SOCKLEN_T 4
+#    define CARES_PULL_SYS_TYPES_H      1
+#    define CARES_PULL_SYS_SOCKET_H     1
 #  endif
 
 #elif defined(__370__)
 #  if defined(__IBMC__) || defined(__IBMCPP__)
 #    if defined(_ILP32)
 #      define CARES_SIZEOF_LONG           4
-#      define CARES_TYPEOF_ARES_SOCKLEN_T FIXME
-#      define CARES_SIZEOF_ARES_SOCKLEN_T -1
 #    elif defined(_LP64)
 #      define CARES_SIZEOF_LONG           8
-#      define CARES_TYPEOF_ARES_SOCKLEN_T FIXME
-#      define CARES_SIZEOF_ARES_SOCKLEN_T -1
 #    endif
+#    define CARES_TYPEOF_ARES_SOCKLEN_T socklen_t
+#    define CARES_SIZEOF_ARES_SOCKLEN_T 4
+#    define CARES_PULL_SYS_TYPES_H      1
+#    define CARES_PULL_SYS_SOCKET_H     1
 #  endif
 
 #elif defined(TPF)
@@ -230,6 +230,18 @@
    Error Compilation_aborted_Unknown_non_configure_build_target
 #endif
 
+/* CARES_PULL_SYS_TYPES_H is defined above when inclusion of header file  */
+/* sys/types.h is required here to properly make type definitions below.  */
+#ifdef CARES_PULL_SYS_TYPES_H
+#  include <sys/types.h>
+#endif
+
+/* CARES_PULL_SYS_SOCKET_H is defined above when inclusion of header file  */
+/* sys/socket.h is required here to properly make type definitions below.  */
+#ifdef CARES_PULL_SYS_SOCKET_H
+#  include <sys/socket.h>
+#endif
+
 /* Data type definition of ares_socklen_t. */
 
 #ifdef CARES_TYPEOF_ARES_SOCKLEN_T