diff --git a/ChangeLog b/ChangeLog
index 0274117f0a..df2aa45fa3 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,8 @@
+Sat Feb  9 11:09:26 2008  Tanaka Akira  <akr@fsij.org>
+
+	* missing/xlgamma_r.c (lgamma_r): return HUGE_VAL for non-positive
+	  integers.
+
 Sat Feb  9 10:03:07 2008  Tanaka Akira  <akr@fsij.org>
 
 	* string.c (rb_str_new4): copy encoding from orig, instead of shared
diff --git a/missing/lgamma_r.c b/missing/lgamma_r.c
index d4402c67b1..ab6c28294a 100644
--- a/missing/lgamma_r.c
+++ b/missing/lgamma_r.c
@@ -12,6 +12,7 @@ reference - Haruhiko Okumura: C-gengo niyoru saishin algorithm jiten
     gamma.c -- Gamma function
 ***********************************************************/
 #include <math.h>
+#include <errno.h>
 #define PI      3.14159265358979324  /* $\pi$ */
 #define LOG_2PI 1.83787706640934548  /* $\log 2\pi$ */
 #define LOG_PI  1.14472988584940017  /* $\log_e \pi$ */
@@ -47,13 +48,13 @@ loggamma(double x)  /* the natural logarithm of the Gamma function. */
 double
 lgamma_r(double x, int *signp)
 {
-    if (x < 0) {
+    if (x <= 0) {
         double i, f, s;
         f = modf(-x, &i);
-        if (f == 0.0) {
-            static const double zero = 0.0;
+        if (f == 0.0) { /* pole error */
             *signp = 1;
-            return 1.0/zero;
+            errno = ERANGE;
+            return HUGE_VAL;
         }
         *signp = (fmod(i, 2.0) != 0.0) ? 1 : -1;
         s = sin(PI * f);