diff --git ruby-clean/configure.ac ruby-workdir/configure.ac
index fced42e..f7563a5 100644
--- ruby-clean/configure.ac
+++ ruby-workdir/configure.ac
@@ -1287,6 +1287,10 @@ main()
 		ac_cv_func_round=no
 		ac_cv_func___builtin_setjmp=no
 		],
+[astral*],[
+		RUBY_APPEND_OPTIONS(CFLAGS, -D_XOPEN_SOURCE -D_GNU_SOURCE)
+		RUBY_APPEND_OPTIONS(CPPFLAGS, -D_XOPEN_SOURCE -D_GNU_SOURCE)
+		],
 [linux*],[	LIBS="-lm $LIBS"
 		# __builtin_longjmp in ppc64* Linux does not restore
 		# the TOC register (r2), which is problematic
diff --git ruby-clean/math.c ruby-workdir/math.c
index 2394fe9..7266696 100644
--- ruby-clean/math.c
+++ ruby-workdir/math.c
@@ -9,6 +9,11 @@
 
 **********************************************************************/
 
+double __lgamma_r(double, int *);
+double lgamma_r(double v, int *p) {
+	return __lgamma_r(v, p);
+}
+
 #include "ruby/internal/config.h"
 
 #ifdef _MSC_VER