diff --git a/Perspex.Controls/Perspex.Controls.csproj b/Perspex.Controls/Perspex.Controls.csproj
index 94392d744f..35400cf22e 100644
--- a/Perspex.Controls/Perspex.Controls.csproj
+++ b/Perspex.Controls/Perspex.Controls.csproj
@@ -60,7 +60,7 @@
     <Compile Include="Platform\IPopupImpl.cs" />
     <Compile Include="Platform\ITopLevelImpl.cs" />
     <Compile Include="PlacementMode.cs" />
-    <Compile Include="Popup.cs" />
+    <Compile Include="Primitives\Popup.cs" />
     <Compile Include="Templates\ControlTemplate`2.cs" />
     <Compile Include="Templates\DataTemplate`1.cs" />
     <Compile Include="Templates\IControlTemplate.cs" />
@@ -126,7 +126,7 @@
     <Compile Include="Utils\IEnumerableUtils.cs" />
     <Compile Include="Utils\StringUtils.cs" />
     <Compile Include="TopLevel.cs" />
-    <Compile Include="PopupRoot.cs" />
+    <Compile Include="Primitives\PopupRoot.cs" />
     <Compile Include="Window.cs" />
     <Compile Include="RowDefinition.cs" />
     <Compile Include="RowDefinitions.cs" />
diff --git a/Perspex.Controls/Popup.cs b/Perspex.Controls/Primitives/Popup.cs
similarity index 99%
rename from Perspex.Controls/Popup.cs
rename to Perspex.Controls/Primitives/Popup.cs
index fb71de2b40..a62ed04096 100644
--- a/Perspex.Controls/Popup.cs
+++ b/Perspex.Controls/Primitives/Popup.cs
@@ -4,7 +4,7 @@
 // </copyright>
 // -----------------------------------------------------------------------
 
-namespace Perspex.Controls
+namespace Perspex.Controls.Primitives
 {
     using System;
     using Perspex.Interactivity;
diff --git a/Perspex.Controls/PopupRoot.cs b/Perspex.Controls/Primitives/PopupRoot.cs
similarity index 98%
rename from Perspex.Controls/PopupRoot.cs
rename to Perspex.Controls/Primitives/PopupRoot.cs
index 8a3891f9e4..eb1e5b4b05 100644
--- a/Perspex.Controls/PopupRoot.cs
+++ b/Perspex.Controls/Primitives/PopupRoot.cs
@@ -4,7 +4,7 @@
 // </copyright>
 // -----------------------------------------------------------------------
 
-namespace Perspex.Controls
+namespace Perspex.Controls.Primitives
 {
     using System;
     using Collections;
diff --git a/Perspex.Controls/ToolTip.cs b/Perspex.Controls/ToolTip.cs
index 7cc596c782..7d2289f712 100644
--- a/Perspex.Controls/ToolTip.cs
+++ b/Perspex.Controls/ToolTip.cs
@@ -6,11 +6,12 @@
 
 namespace Perspex.Controls
 {
-    using Perspex.Input;
-    using Perspex.Threading;
     using System;
     using System.Reactive.Linq;
     using System.Reactive.Subjects;
+    using Perspex.Controls.Primitives;
+    using Perspex.Input;
+    using Perspex.Threading;
 
     /// <summary>
     /// A tooltip control.
diff --git a/Perspex.Themes.Default/PopupRootStyle.cs b/Perspex.Themes.Default/PopupRootStyle.cs
index a89ad104c7..75b3d5c6a3 100644
--- a/Perspex.Themes.Default/PopupRootStyle.cs
+++ b/Perspex.Themes.Default/PopupRootStyle.cs
@@ -9,6 +9,7 @@ namespace Perspex.Themes.Default
     using System.Linq;
     using Perspex.Controls;
     using Perspex.Controls.Presenters;
+    using Perspex.Controls.Primitives;
     using Perspex.Controls.Templates;
     using Perspex.Styling;
 
diff --git a/Tests/Perspex.Controls.UnitTests/Perspex.Controls.UnitTests.csproj b/Tests/Perspex.Controls.UnitTests/Perspex.Controls.UnitTests.csproj
index 867a1230ec..d094f34ffc 100644
--- a/Tests/Perspex.Controls.UnitTests/Perspex.Controls.UnitTests.csproj
+++ b/Tests/Perspex.Controls.UnitTests/Perspex.Controls.UnitTests.csproj
@@ -93,7 +93,7 @@
     <Compile Include="GlobalSuppressions.cs" />
     <Compile Include="Mixins\SelectableMixinTests.cs" />
     <Compile Include="Parsers\GridLengthsParserTests.cs" />
-    <Compile Include="PopupTests.cs" />
+    <Compile Include="Primitives\PopupTests.cs" />
     <Compile Include="DropDownTests.cs" />
     <Compile Include="Presenters\DeckPresenterTests.cs" />
     <Compile Include="Presenters\ItemsPresenterTests.cs" />
diff --git a/Tests/Perspex.Controls.UnitTests/PopupTests.cs b/Tests/Perspex.Controls.UnitTests/Primitives/PopupTests.cs
similarity index 97%
rename from Tests/Perspex.Controls.UnitTests/PopupTests.cs
rename to Tests/Perspex.Controls.UnitTests/Primitives/PopupTests.cs
index 0c09e46d7d..887c3eed5b 100644
--- a/Tests/Perspex.Controls.UnitTests/PopupTests.cs
+++ b/Tests/Perspex.Controls.UnitTests/Primitives/PopupTests.cs
@@ -4,10 +4,11 @@
 // </copyright>
 // -----------------------------------------------------------------------
 
-namespace Perspex.Controls.UnitTests
+namespace Perspex.Controls.UnitTests.Primitives
 {
     using System.Collections.Specialized;
     using System.Linq;
+    using Perspex.Controls.Primitives;
     using Perspex.LogicalTree;
     using Xunit;