diff --git a/ChangeLog b/ChangeLog
index ff3e466a23..0599328997 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,9 @@
+Tue Jun 22 23:35:43 2004  NAKAMURA Usaku  <usa@ruby-lang.org>
+
+	* sprintf.c (rb_f_sprintf): support FZERO and FSPACE with NaN/Inf.
+
+	* test/ruby/test_sprintf.rb (test_nan, test_inf): add tests.
+
 Tue Jun 22 21:11:36 2004  Masaki Suketa  <masaki.suketa@nifty.ne.jp>
 
 	* ext/win32ole/win32ole.c (OLE_FREE): should not call CoFreeUnuse-
diff --git a/sprintf.c b/sprintf.c
index be22578a8d..17bcce1330 100644
--- a/sprintf.c
+++ b/sprintf.c
@@ -698,7 +698,7 @@ rb_f_sprintf(argc, argv)
 			expr = "Inf";
 		    }
 		    need = strlen(expr);
-		    if (fval < 0.0 || (flags & FPLUS))
+		    if ((!isnan(fval) && fval < 0.0) || (flags & FPLUS))
 			need++;
 		    if ((flags & FWIDTH) && need < width)
 			need = width;
@@ -706,14 +706,34 @@ rb_f_sprintf(argc, argv)
 		    CHECK(need);
 		    sprintf(&buf[blen], "%*s", need, "");
 		    if (flags & FMINUS) {
-			if (fval < 0.0)
+			if (!isnan(fval) && fval < 0.0)
 			    buf[blen++] = '-';
 			else if (flags & FPLUS)
 			    buf[blen++] = '+';
+			else if (flags & FSPACE)
+			    blen++;
+			strncpy(&buf[blen], expr, strlen(expr));
+		    }
+		    else if (flags & FZERO) {
+			if (!isnan(fval) && fval < 0.0) {
+			    buf[blen++] = '-';
+			    need--;
+			}
+			else if (flags & FPLUS) {
+			    buf[blen++] = '+';
+			    need--;
+			}
+			else if (flags & FSPACE) {
+			    blen++;
+			    need--;
+			}
+			while (need-- - strlen(expr) > 0) {
+			    buf[blen++] = '0';
+			}
 			strncpy(&buf[blen], expr, strlen(expr));
 		    }
 		    else {
-			if (fval < 0.0)
+			if (!isnan(fval) && fval < 0.0)
 			    buf[blen + need - strlen(expr) - 1] = '-';
 			else if (flags & FPLUS)
 			    buf[blen + need - strlen(expr) - 1] = '+';
diff --git a/test/ruby/test_sprintf.rb b/test/ruby/test_sprintf.rb
index 8716e7021d..c72eadb218 100644
--- a/test/ruby/test_sprintf.rb
+++ b/test/ruby/test_sprintf.rb
@@ -72,4 +72,70 @@ class TestSprintf < Test::Unit::TestCase
     assert_equal(" +0010", sprintf("%+6.4b", 2))
     assert_equal(" -0001", sprintf("%+6.4b", -1))
   end
+
+  def test_nan
+    nan = 0.0 / 0.0
+    assert_equal("NaN", sprintf("%f", nan))
+    assert_equal("NaN", sprintf("%-f", nan))
+    assert_equal("+NaN", sprintf("%+f", nan))
+
+    assert_equal("     NaN", sprintf("%8f", nan))
+    assert_equal("NaN     ", sprintf("%-8f", nan))
+    assert_equal("    +NaN", sprintf("%+8f", nan))
+
+    assert_equal("00000NaN", sprintf("%08f", nan))
+    assert_equal("NaN     ", sprintf("%-08f", nan))
+    assert_equal("+0000NaN", sprintf("%+08f", nan))
+
+    assert_equal("     NaN", sprintf("% 8f", nan))
+    assert_equal(" NaN    ", sprintf("%- 8f", nan))
+    assert_equal("    +NaN", sprintf("%+ 8f", nan))
+
+    assert_equal(" 0000NaN", sprintf("% 08f", nan))
+    assert_equal(" NaN    ", sprintf("%- 08f", nan))
+    assert_equal("+0000NaN", sprintf("%+ 08f", nan))
+  end
+
+  def test_inf
+    inf = 1.0 / 0.0
+    assert_equal("Inf", sprintf("%f", inf))
+    assert_equal("Inf", sprintf("%-f", inf))
+    assert_equal("+Inf", sprintf("%+f", inf))
+
+    assert_equal("     Inf", sprintf("%8f", inf))
+    assert_equal("Inf     ", sprintf("%-8f", inf))
+    assert_equal("    +Inf", sprintf("%+8f", inf))
+
+    assert_equal("00000Inf", sprintf("%08f", inf))
+    assert_equal("Inf     ", sprintf("%-08f", inf))
+    assert_equal("+0000Inf", sprintf("%+08f", inf))
+
+    assert_equal("     Inf", sprintf("% 8f", inf))
+    assert_equal(" Inf    ", sprintf("%- 8f", inf))
+    assert_equal("    +Inf", sprintf("%+ 8f", inf))
+
+    assert_equal(" 0000Inf", sprintf("% 08f", inf))
+    assert_equal(" Inf    ", sprintf("%- 08f", inf))
+    assert_equal("+0000Inf", sprintf("%+ 08f", inf))
+
+    assert_equal("-Inf", sprintf("%f", -inf))
+    assert_equal("-Inf", sprintf("%-f", -inf))
+    assert_equal("-Inf", sprintf("%+f", -inf))
+
+    assert_equal("    -Inf", sprintf("%8f", -inf))
+    assert_equal("-Inf    ", sprintf("%-8f", -inf))
+    assert_equal("    -Inf", sprintf("%+8f", -inf))
+
+    assert_equal("-0000Inf", sprintf("%08f", -inf))
+    assert_equal("-Inf    ", sprintf("%-08f", -inf))
+    assert_equal("-0000Inf", sprintf("%+08f", -inf))
+
+    assert_equal("    -Inf", sprintf("% 8f", -inf))
+    assert_equal("-Inf    ", sprintf("%- 8f", -inf))
+    assert_equal("    -Inf", sprintf("%+ 8f", -inf))
+
+    assert_equal("-0000Inf", sprintf("% 08f", -inf))
+    assert_equal("-Inf    ", sprintf("%- 08f", -inf))
+    assert_equal("-0000Inf", sprintf("%+ 08f", -inf))
+  end
 end