Attempt to fix OpenIndiana build issue introduced by #19922
diff --git a/configure b/configure
index 6bcc4b5..101dd44 100755
--- a/configure
+++ b/configure
@@ -3447,12 +3447,18 @@
 
 # On HP-UX mbstate_t requires _INCLUDE__STDC_A1_SOURCE
 case $ac_sys_system in
-hp*|HP*)
+  hp*|HP*)
+    define_stdc_a1=yes;;
+  *)
+    define_stdc_a1=no;;
+esac
+
+if test $define_stdc_a1 = yes
+then
 
 $as_echo "#define _INCLUDE__STDC_A1_SOURCE 1" >>confdefs.h
 
-  ;;
-esac
+fi
 
 #
 # SGI compilers allow the specification of the both the ABI and the
diff --git a/configure.ac b/configure.ac
index 2d701b1..25e1dc8 100644
--- a/configure.ac
+++ b/configure.ac
@@ -524,11 +524,17 @@
 
 # On HP-UX mbstate_t requires _INCLUDE__STDC_A1_SOURCE
 case $ac_sys_system in
-hp*|HP*)
-  AC_DEFINE(_INCLUDE__STDC_A1_SOURCE, 1, Define to include mbstate_t for mbrtowc)
-  ;;
+  hp*|HP*)
+    define_stdc_a1=yes;;
+  *)
+    define_stdc_a1=no;;
 esac
 
+if test $define_stdc_a1 = yes
+then
+  AC_DEFINE(_INCLUDE__STDC_A1_SOURCE, 1, Define to include mbstate_t for mbrtowc)
+fi
+
 #
 # SGI compilers allow the specification of the both the ABI and the
 # ISA on the command line.  Depending on the values of these switches,