diff --git a/libcore/luni/src/main/java/java/lang/StrictMath.java b/libcore/luni/src/main/java/java/lang/StrictMath.java
index cd3c9b5..5c6ebc7 100644
--- a/libcore/luni/src/main/java/java/lang/StrictMath.java
+++ b/libcore/luni/src/main/java/java/lang/StrictMath.java
@@ -1042,7 +1042,9 @@
      * @since 1.6
      * @hide
      */
-    public static native double copySign(double magnitude, double sign);
+    public static double copySign(double magnitude, double sign) {
+        return Math.copySign(magnitude, sign);
+    }
 
     /**
      * Returns a float with the given magnitude and the sign of {@code sign}.
@@ -1050,7 +1052,9 @@
      * @since 1.6
      * @hide
      */
-    public static native float copySign(float magnitude, float sign);
+    public static float copySign(float magnitude, float sign) {
+        return Math.copySign(magnitude, sign);
+    }
 
     /**
      * Answers the exponent of a float.
diff --git a/libcore/luni/src/main/native/java_lang_Math.c b/libcore/luni/src/main/native/java_lang_Math.c
index 35754cd..90cb9b5 100644
--- a/libcore/luni/src/main/native/java_lang_Math.c
+++ b/libcore/luni/src/main/native/java_lang_Math.c
@@ -160,11 +160,13 @@
 }
 
 static jdouble copySign(JNIEnv* env, jclass clazz, jdouble a, jdouble b) {
-    return copysign(a, b);
+    // Our StrictMath.copySign delegates to Math.copySign, so we need to treat NaN as positive.
+    return copysign(a, isnan(b) ? 1.0 : b);
 }
 
 static jfloat copySign_f(JNIEnv* env, jclass clazz, jfloat a, jfloat b) {
-    return copysignf(a, b);
+    // Our StrictMath.copySign delegates to Math.copySign, so we need to treat NaN as positive.
+    return copysignf(a, isnan(b) ? 1.0 : b);
 }
 
 /*
diff --git a/libcore/luni/src/main/native/java_lang_StrictMath.c b/libcore/luni/src/main/native/java_lang_StrictMath.c
index 3839c21..cb0f87e 100644
--- a/libcore/luni/src/main/native/java_lang_StrictMath.c
+++ b/libcore/luni/src/main/native/java_lang_StrictMath.c
@@ -20,8 +20,6 @@
 #include "../../external/fdlibm/fdlibm.h"
 _LIB_VERSION_TYPE _LIB_VERSION = _IEEE_;
 
-#include <math.h>
-
 /* native public static double sin(double a); */
 static jdouble jsin(JNIEnv* env, jclass clazz, jdouble a)
 {
@@ -186,14 +184,6 @@
     return arg1;
 }
 
-static jdouble copySign(JNIEnv* env, jclass clazz, jdouble a, jdouble b) {
-    return copysign(a, isnan(b) ? 1.0 : b);
-}
-
-static jfloat copySign_f(JNIEnv* env, jclass clazz, jfloat a, jfloat b) {
-    return copysignf(a, isnan(b) ? 1.0f : b);
-}
-
 /*
  * JNI registration.
  */
@@ -206,8 +196,6 @@
     { "atan2",  "(DD)D", jatan2 },
     { "cbrt",   "(D)D", jcbrt },
     { "ceil",   "(D)D", jceil },
-    { "copySign",  "(DD)D", copySign },
-    { "copySign",  "(FF)F", copySign_f },
     { "cos",    "(D)D", jcos },
     { "cosh",   "(D)D", jcosh },
     { "exp",    "(D)D", jexp },