diff --git a/ChangeLog b/ChangeLog
index 8f768b2f57..d64a3d2729 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,8 @@
+Sat Mar 29 17:54:46 2003  Yukihiro Matsumoto  <matz@ruby-lang.org>
+
+	* pack.c (pack_pack): do not call rb_str_buf_cat() with NULL ptr,
+	  which causes SEGV; jump to grow instead. [ruby-dev:19944]
+
 Sat Mar 29 15:19:48 2003  Tanaka Akira  <akr@m17n.org>
 
         * instruby.rb, ext/extmk.rb, lib/benchmark.rb, lib/cgi.rb,
diff --git a/pack.c b/pack.c
index be89a0942f..000c6e5ca9 100644
--- a/pack.c
+++ b/pack.c
@@ -489,7 +489,8 @@ pack_pack(ary, fmt)
 			c = byte & 0xff;
 			rb_str_buf_cat(res, &c, 1);
 		    }
-		    rb_str_buf_cat(res, 0, j);
+		    len = j;
+		    goto grow;
 		}
 		break;
 
@@ -518,7 +519,8 @@ pack_pack(ary, fmt)
 			c = byte & 0xff;
 			rb_str_buf_cat(res, &c, 1);
 		    }
-		    rb_str_buf_cat(res, 0, j);
+		    len = j;
+		    goto grow;
 		}
 		break;
 
@@ -548,7 +550,8 @@ pack_pack(ary, fmt)
 			char c = byte & 0xff;
 			rb_str_buf_cat(res, &c, 1);
 		    }
-		    rb_str_buf_cat(res, 0, j);
+		    len = 1;
+		    goto grow;
 		}
 		break;
 
@@ -578,7 +581,8 @@ pack_pack(ary, fmt)
 			char c = byte & 0xff;
 			rb_str_buf_cat(res, &c, 1);
 		    }
-		    rb_str_buf_cat(res, 0, j);
+		    len = j;
+		    goto grow;
 		}
 		break;
 	    }