diff --git a/content/base/public/nsContentUtils.h b/content/base/public/nsContentUtils.h
index bcfb9dca43b4..07f953c5874f 100644
--- a/content/base/public/nsContentUtils.h
+++ b/content/base/public/nsContentUtils.h
@@ -42,8 +42,12 @@
 #ifndef nsContentUtils_h___
 #define nsContentUtils_h___
 
+#include <math.h>
+#if defined(XP_WIN) || defined(XP_OS2)
+#include <float.h>
+#endif
+
 #include "jsprvtd.h"
-#include "jsnum.h"
 #include "nsAString.h"
 #include "nsIStatefulFrame.h"
 #include "nsINodeInfo.h"
@@ -1711,20 +1715,14 @@ private:
 
 /*
  * Check whether a floating point number is finite (not +/-infinity and not a
- * NaN value). We wrap JSDOUBLE_IS_FINITE in a function because it expects to
- * take the address of its argument, and because the argument must be of type
- * jsdouble to have the right size and layout of bits.
- *
- * Note: we could try to exploit the fact that |infinity - infinity == NaN|
- * instead of using JSDOUBLE_IS_FINITE. This would produce more compact code
- * and perform better by avoiding type conversions and bit twiddling.
- * Unfortunately, some architectures don't guarantee that |f == f| evaluates
- * to true (where f is any *finite* floating point number). See
- * https://bugzilla.mozilla.org/show_bug.cgi?id=369418#c63 . To play it safe
- * for gecko 1.9, we just reuse JSDOUBLE_IS_FINITE.
+ * NaN value).
  */
 inline NS_HIDDEN_(PRBool) NS_FloatIsFinite(jsdouble f) {
-  return JSDOUBLE_IS_FINITE(f);
+#ifdef WIN32
+  return _finite(f);
+#else
+  return finite(f);
+#endif
 }
 
 /*
diff --git a/content/canvas/src/nsCanvasRenderingContext2D.cpp b/content/canvas/src/nsCanvasRenderingContext2D.cpp
index 5bc97e02ed94..e29c95913de2 100644
--- a/content/canvas/src/nsCanvasRenderingContext2D.cpp
+++ b/content/canvas/src/nsCanvasRenderingContext2D.cpp
@@ -41,6 +41,9 @@
 #define _USE_MATH_DEFINES
 #endif
 #include <math.h>
+#if defined(XP_WIN) || defined(XP_OS2)
+#include <float.h>
+#endif
 
 #include "prmem.h"
 
@@ -87,7 +90,6 @@
 #include "nsIDocShellTreeNode.h"
 #include "nsIXPConnect.h"
 #include "jsapi.h"
-#include "jsnum.h"
 
 #include "nsTArray.h"
 
@@ -116,7 +118,17 @@ using namespace mozilla;
 
 /* Float validation stuff */
 
-#define VALIDATE(_f)  if (!JSDOUBLE_IS_FINITE(_f)) return PR_FALSE
+static inline bool
+DoubleIsFinite(double d)
+{
+#ifdef WIN32
+    return _finite(d);
+#else
+    return finite(d);
+#endif
+}
+
+#define VALIDATE(_f)  if (!DoubleIsFinite(_f)) return PR_FALSE
 
 /* These must take doubles as args, because JSDOUBLE_IS_FINITE expects
  * to take the address of its argument; we can't cast/convert in the
diff --git a/dom/base/nsDOMClassInfo.cpp b/dom/base/nsDOMClassInfo.cpp
index d22126de19c1..0f5889722281 100644
--- a/dom/base/nsDOMClassInfo.cpp
+++ b/dom/base/nsDOMClassInfo.cpp
@@ -67,7 +67,6 @@
 #include "jsprvtd.h"    // we are using private JS typedefs...
 #include "jscntxt.h"
 #include "jsdbgapi.h"
-#include "jsnum.h"
 
 // General helper includes
 #include "nsGlobalWindow.h"
@@ -3825,7 +3824,7 @@ nsDOMClassInfo::GetArrayIndexFromId(JSContext *cx, jsval id, PRBool *aIsNumber)
 
   jsint i = -1;
 
-  if (!JSDOUBLE_IS_INT(array_index, i)) {
+  if (!::JS_DoubleIsInt32(array_index, &i)) {
     return -1;
   }
 
diff --git a/dom/src/json/nsJSON.cpp b/dom/src/json/nsJSON.cpp
index 6cb362774204..b4963f88ac29 100644
--- a/dom/src/json/nsJSON.cpp
+++ b/dom/src/json/nsJSON.cpp
@@ -40,7 +40,6 @@
 #include "jsapi.h"
 #include "jsdtoa.h"
 #include "jsprvtd.h"
-#include "jsnum.h"
 #include "jsbool.h"
 #include "jsarena.h"
 #include "jscntxt.h"
diff --git a/js/src/Makefile.in b/js/src/Makefile.in
index 50b079ec5ce9..ca475544f0b6 100644
--- a/js/src/Makefile.in
+++ b/js/src/Makefile.in
@@ -193,7 +193,6 @@ INSTALLED_HEADERS = \
 		jslock.h \
 		jslong.h \
 		jsmath.h \
-		jsnum.h \
 		jsobj.h \
 		jsobjinlines.h \
 		json.h \
diff --git a/js/src/jsapi.cpp b/js/src/jsapi.cpp
index 17f69069cb0e..300b4b69c177 100644
--- a/js/src/jsapi.cpp
+++ b/js/src/jsapi.cpp
@@ -443,6 +443,12 @@ JS_ValueToNumber(JSContext *cx, jsval v, jsdouble *dp)
     return !JSVAL_IS_NULL(tvr.value());
 }
 
+JS_PUBLIC_API(JSBool)
+JS_DoubleIsInt32(jsdouble d, jsint *ip)
+{
+    return JSDOUBLE_IS_INT(d, *ip);
+}
+
 JS_PUBLIC_API(JSBool)
 JS_ValueToECMAInt32(JSContext *cx, jsval v, int32 *ip)
 {
diff --git a/js/src/jsapi.h b/js/src/jsapi.h
index 6e0fdbd12e41..818be2610920 100644
--- a/js/src/jsapi.h
+++ b/js/src/jsapi.h
@@ -467,6 +467,9 @@ JS_ValueToSource(JSContext *cx, jsval v);
 extern JS_PUBLIC_API(JSBool)
 JS_ValueToNumber(JSContext *cx, jsval v, jsdouble *dp);
 
+extern JS_PUBLIC_API(JSBool)
+JS_DoubleIsInt32(jsdouble d, jsint *ip);
+
 /*
  * Convert a value to a number, then to an int32, according to the ECMA rules
  * for ToInt32.