diff --git a/include/curl/system.h b/include/curl/system.h
index eac4cfeb66..ef4fdca417 100644
--- a/include/curl/system.h
+++ b/include/curl/system.h
@@ -320,6 +320,24 @@
 #  define CURL_PULL_SYS_TYPES_H      1
 #  define CURL_PULL_SYS_SOCKET_H     1
 
+#elif defined(__xlc__) /* IBM xlc compiler */
+#  if !defined(_LP64)
+#    define CURL_TYPEOF_CURL_OFF_T     long long
+#    define CURL_FORMAT_CURL_OFF_T     "lld"
+#    define CURL_FORMAT_CURL_OFF_TU    "llu"
+#    define CURL_SUFFIX_CURL_OFF_T     LL
+#    define CURL_SUFFIX_CURL_OFF_TU    ULL
+#  else
+#    define CURL_TYPEOF_CURL_OFF_T     long
+#    define CURL_FORMAT_CURL_OFF_T     "ld"
+#    define CURL_FORMAT_CURL_OFF_TU    "lu"
+#    define CURL_SUFFIX_CURL_OFF_T     L
+#    define CURL_SUFFIX_CURL_OFF_TU    UL
+#  endif
+#  define CURL_TYPEOF_CURL_SOCKLEN_T socklen_t
+#  define CURL_PULL_SYS_TYPES_H      1
+#  define CURL_PULL_SYS_SOCKET_H     1
+
 /* ===================================== */
 /*    KEEP MSVC THE PENULTIMATE ENTRY    */
 /* ===================================== */