diff --git a/src/Microsoft.AspNet.Server.Kestrel/Networking/Libuv.cs b/src/Microsoft.AspNet.Server.Kestrel/Networking/Libuv.cs
index ef6fb74434..f00bfa586e 100644
--- a/src/Microsoft.AspNet.Server.Kestrel/Networking/Libuv.cs
+++ b/src/Microsoft.AspNet.Server.Kestrel/Networking/Libuv.cs
@@ -10,11 +10,11 @@ namespace Microsoft.AspNet.Server.Kestrel.Networking
     {
         public Libuv()
         {
-            IsWindows = PlatformApis.IsWindows();
+            IsWindows = PlatformApis.IsWindows;
 
             var isDarwinMono =
 #if DNX451
-                IsWindows ? false : PlatformApis.IsDarwin();
+                IsWindows ? false : PlatformApis.IsDarwin;
 #else
                 false;
 #endif
diff --git a/src/Microsoft.AspNet.Server.Kestrel/Networking/PlatformApis.cs b/src/Microsoft.AspNet.Server.Kestrel/Networking/PlatformApis.cs
index f874ac9b15..370fcb30c2 100644
--- a/src/Microsoft.AspNet.Server.Kestrel/Networking/PlatformApis.cs
+++ b/src/Microsoft.AspNet.Server.Kestrel/Networking/PlatformApis.cs
@@ -8,23 +8,25 @@ namespace Microsoft.AspNet.Server.Kestrel.Networking
 {
     public static class PlatformApis
     {
-        public static bool IsWindows()
+        static PlatformApis()
         {
 #if DOTNET5_4 || DNXCORE50
-            // Until Environment.OSVersion.Platform is exposed on .NET Core, we
-            // try to call uname and if that fails we assume we are on Windows.
-            return GetUname() == string.Empty;
+            IsWindows = RuntimeInformation.IsOSPlatform(OSPlatform.Windows);
+            IsDarwin = RuntimeInformation.IsOSPlatform(OSPlatform.OSX);
 #else
-            var p = (int)Environment.OSVersion.Platform;
-            return (p != 4) && (p != 6) && (p != 128);
+            var p = (int)System.Environment.OSVersion.Platform;
+            IsWindows = (p != 4) && (p != 6) && (p != 128);
+            
+            // When running on Mono in Darwin OSVersion doesn't return Darwin. It returns Unix instead.
+            // Fallback to use uname.
+            IsDarwin = string.Equals(GetUname(), "Darwin", StringComparison.Ordinal);
 #endif
         }
+        
+        public static bool IsWindows { get; }
 
-        public static bool IsDarwin()
-        {
-            return string.Equals(GetUname(), "Darwin", StringComparison.Ordinal);
-        }
-
+        public static bool IsDarwin { get; }
+        
         [DllImport("libc")]
         static extern int uname(IntPtr buf);
 
diff --git a/src/Microsoft.AspNet.Server.Kestrel/Networking/SockAddr.cs b/src/Microsoft.AspNet.Server.Kestrel/Networking/SockAddr.cs
index 3be4ee9301..762b1f5140 100644
--- a/src/Microsoft.AspNet.Server.Kestrel/Networking/SockAddr.cs
+++ b/src/Microsoft.AspNet.Server.Kestrel/Networking/SockAddr.cs
@@ -64,7 +64,7 @@ namespace Microsoft.AspNet.Server.Kestrel.Networking
             var port = ((int)(_field0 & 0x00FF0000) >> 8) | (int)((_field0 & 0xFF000000) >> 24);
             
             int family = (int)_field0;
-            if (PlatformApis.IsDarwin())
+            if (PlatformApis.IsDarwin)
             {
                 // see explaination in example 4
                 family = family >> 8;