diff --git a/src/platform-freebsd.cc b/src/platform-freebsd.cc
index 9b452fa9e6..353d165403 100644
--- a/src/platform-freebsd.cc
+++ b/src/platform-freebsd.cc
@@ -89,11 +89,6 @@ uint64_t OS::CpuFeaturesImpliedByPlatform() {
 }
 
 
-double OS::nan_value() {
-  return NAN;
-}
-
-
 int OS::ActivationFrameAlignment() {
   // 16 byte alignment on FreeBSD
   return 16;
diff --git a/src/platform-linux.cc b/src/platform-linux.cc
index 9ce0be011b..bfcd8fba72 100644
--- a/src/platform-linux.cc
+++ b/src/platform-linux.cc
@@ -95,11 +95,6 @@ uint64_t OS::CpuFeaturesImpliedByPlatform() {
 }
 
 
-double OS::nan_value() {
-  return NAN;
-}
-
-
 #ifdef __arm__
 bool OS::ArmCpuHasFeature(CpuFeature feature) {
   const char* search_string = NULL;
diff --git a/src/platform-macos.cc b/src/platform-macos.cc
index d79cff14ac..0d5be45eec 100644
--- a/src/platform-macos.cc
+++ b/src/platform-macos.cc
@@ -252,11 +252,6 @@ uint64_t OS::CpuFeaturesImpliedByPlatform() {
 }
 
 
-double OS::nan_value() {
-  return NAN;
-}
-
-
 int OS::ActivationFrameAlignment() {
   // OS X activation frames must be 16 byte-aligned; see "Mac OS X ABI
   // Function Call Guide".
diff --git a/src/platform-openbsd.cc b/src/platform-openbsd.cc
index 204d3b7bc5..6d273047da 100644
--- a/src/platform-openbsd.cc
+++ b/src/platform-openbsd.cc
@@ -88,11 +88,6 @@ uint64_t OS::CpuFeaturesImpliedByPlatform() {
 }
 
 
-double OS::nan_value() {
-  return NAN;
-}
-
-
 int OS::ActivationFrameAlignment() {
   // 16 byte alignment on OpenBSD
   return 16;
diff --git a/src/platform-posix.cc b/src/platform-posix.cc
index 056ebd20ff..41e0e64f3b 100644
--- a/src/platform-posix.cc
+++ b/src/platform-posix.cc
@@ -61,6 +61,13 @@ double modulo(double x, double y) {
   return fmod(x, y);
 }
 
+
+double OS::nan_value() {
+  // NAN from math.h is defined in C99 and not in POSIX.
+  return NAN;
+}
+
+
 // ----------------------------------------------------------------------------
 // POSIX date/time support.
 //