diff --git a/Octokit.Reactive/Octokit.Reactive.csproj b/Octokit.Reactive/Octokit.Reactive.csproj
index bfe5da0a..79722400 100644
--- a/Octokit.Reactive/Octokit.Reactive.csproj
+++ b/Octokit.Reactive/Octokit.Reactive.csproj
@@ -32,7 +32,7 @@
     <Optimize>true</Optimize>
     <IntermediateOutputPath>obj\Release\Net40</IntermediateOutputPath>
     <OutputPath>bin\Release\Net40</OutputPath>
-    <DefineConstants>TRACE</DefineConstants>
+    <DefineConstants>TRACE;NET_45</DefineConstants>
     <ErrorReport>prompt</ErrorReport>
     <WarningLevel>4</WarningLevel>
     <Prefer32Bit>false</Prefer32Bit>
diff --git a/Octokit.Tests/Octokit.Tests.csproj b/Octokit.Tests/Octokit.Tests.csproj
index af4759db..2bec1229 100644
--- a/Octokit.Tests/Octokit.Tests.csproj
+++ b/Octokit.Tests/Octokit.Tests.csproj
@@ -25,7 +25,7 @@
     <DebugType>pdbonly</DebugType>
     <Optimize>true</Optimize>
     <OutputPath>bin\Release\</OutputPath>
-    <DefineConstants>TRACE</DefineConstants>
+    <DefineConstants>TRACE;NET_45</DefineConstants>
     <ErrorReport>prompt</ErrorReport>
     <WarningLevel>4</WarningLevel>
   </PropertyGroup>
diff --git a/Octokit/Octokit.csproj b/Octokit/Octokit.csproj
index ec45f73d..6a070105 100644
--- a/Octokit/Octokit.csproj
+++ b/Octokit/Octokit.csproj
@@ -33,7 +33,7 @@
     <Optimize>true</Optimize>
     <IntermediateOutputPath>obj\Release\Net40</IntermediateOutputPath>
     <OutputPath>bin\Release\Net40</OutputPath>
-    <DefineConstants>TRACE;CODE_ANALYSIS;CODE_ANALYSIS;SIMPLE_JSON_OBJARRAYINTERNAL;SIMPLE_JSON_INTERNAL</DefineConstants>
+    <DefineConstants>TRACE;CODE_ANALYSIS;CODE_ANALYSIS;SIMPLE_JSON_OBJARRAYINTERNAL;SIMPLE_JSON_INTERNAL;NET_45</DefineConstants>
     <ErrorReport>prompt</ErrorReport>
     <WarningLevel>4</WarningLevel>
     <Prefer32Bit>false</Prefer32Bit>