diff --git a/ChangeLog b/ChangeLog
index bfcf9e6bc6..ea952ff13b 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,10 @@
+Fri Oct 12 21:55:08 2012  Hiroshi Shirosaki  <h.shirosaki@gmail.com>
+
+	* include/ruby/win32.h (rb_w32_pow): set floating point precision
+	  for mingw-w64 x86 pow(). This improves the precision of pow() on
+	  Windows XP for TestFloat#test_round_with_precision failure.
+	  [ruby-core:47911] [Bug #7142]
+
 Fri Oct 12 21:37:25 2012  Hiroshi Shirosaki  <h.shirosaki@gmail.com>
 
 	* test/webrick/test_cgi.rb (TestWEBrickCGI#test_cgi): skip a test
diff --git a/include/ruby/win32.h b/include/ruby/win32.h
index 718da1376c..a2eec0cf19 100644
--- a/include/ruby/win32.h
+++ b/include/ruby/win32.h
@@ -764,7 +764,7 @@ uintptr_t rb_w32_asynchronize(asynchronous_func_t func, uintptr_t self, int argc
 }  /* extern "C" { */
 #endif
 
-#ifdef __MINGW64__
+#if defined(__MINGW64__)
 /*
  * Use powl() instead of broken pow() of x86_64-w64-mingw32.
  * This workaround will fix test failures in test_bignum.rb,
@@ -775,6 +775,24 @@ rb_w32_pow(double x, double y)
 {
     return powl(x, y);
 }
+#elif defined(__MINGW64_VERSION_MAJOR)
+/*
+ * Set floating point precision for pow() of mingw-w64 x86.
+ * With default precision the result is not proper on WinXP.
+ */
+static inline double
+rb_w32_pow(double x, double y)
+{
+    double r;
+    unsigned int default_control = _controlfp(0, 0);
+    _controlfp(_PC_64, _MCW_PC);
+    r = pow(x, y);
+    /* Restore setting */
+    _controlfp(default_control, _MCW_PC);
+    return r;
+}
+#endif
+#if defined(__MINGW64_VERSION_MAJOR) || defined(__MINGW64__)
 #define pow rb_w32_pow
 #endif