diff --git a/acinclude.m4 b/acinclude.m4
index 64c96298680093ff380916b12c181f1bb1f6fb41..60606d2c006204307169784694cdd0f45a960830 100644
--- a/acinclude.m4
+++ b/acinclude.m4
@@ -22,7 +22,7 @@ PKG_FFLAGS=`"${R_HOME}/bin/R" CMD config FFLAGS`
 
 
 case "${host}" in
-  *-sun-solaris*) 
+  x*-sun-solaris*) 
 dnl use a hard coded call to src/tripack.f through R
 dnl to determine wether it returns all NA. 
 dnl then retry with -xO5