diff --git a/acinclude.m4 b/acinclude.m4
index f959bfbe65..352b19c7e8 100644
--- a/acinclude.m4
+++ b/acinclude.m4
@@ -152,6 +152,9 @@ case $system in
                 AC_MSG_RESULT(hp_ux)
                 ;;
         *-irix*)
+		if test -d /usr/include/SN/SN1; then
+		 IRIX_BUILD_IP35="IP35"
+		fi
 		MKAFS_OSTYPE=IRIX
                 AC_MSG_RESULT(sgi)
                 ;;
@@ -483,6 +486,7 @@ AC_SUBST(DEST)
 AC_SUBST(WITH_OBSOLETE)
 AC_SUBST(WITH_INSECURE)
 AC_SUBST(DARWIN_INFOFILE)
+AC_SUBST(IRIX_BUILD_IP35)
 
 OPENAFS_OSCONF
 
diff --git a/src/libafs/MakefileProto.IRIX.in b/src/libafs/MakefileProto.IRIX.in
index 9cb5612da7..180971e4eb 100644
--- a/src/libafs/MakefileProto.IRIX.in
+++ b/src/libafs/MakefileProto.IRIX.in
@@ -213,7 +213,7 @@ PROCESSORS = R5000 R1000
 <sgi_64>
 PROCESSORS = R10000
 <sgi_65>
-PROCESSORS = IP19 IP20 IP21 IP25 IP26 IP27 IP28 IP30 IP35
+PROCESSORS = IP19 IP20 IP21 IP25 IP26 IP27 IP28 IP30 @IRIX_BUILD_IP35@
 <all>
 
 KOBJ = STATIC MODLOAD