diff --git a/ChangeLog b/ChangeLog
index 2df68499a1..ac7ec8a557 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,7 @@
+Mon Jul  8 08:03:01 2013  Tanaka Akira  <akr@fsij.org>
+
+	* bignum.c (bary_mul): Add a RB_GC_GUARD.
+
 Sun Jul  7 23:56:32 2013  Tanaka Akira  <akr@fsij.org>
 
 	* bignum.c (bary_mul_karatsuba): Unreachable code removed.  Remove
diff --git a/bignum.c b/bignum.c
index 4c1c5f74a1..834bbc1eb8 100644
--- a/bignum.c
+++ b/bignum.c
@@ -1867,6 +1867,7 @@ bary_mul(BDIGIT *zds, size_t zl, BDIGIT *xds, size_t xl, BDIGIT *yds, size_t yl)
         z = bigtrunc(bigmul1_toom3(x, y));
         MEMCPY(zds, BDIGITS(z), BDIGIT, RBIGNUM_LEN(z));
         MEMZERO(zds + RBIGNUM_LEN(z), BDIGIT, zl - RBIGNUM_LEN(z));
+        RB_GC_GUARD(z);
     }
 }