diff --git a/src/SourceGenerators/Uno.UI.SourceGenerators/XamlGenerator/XamlCodeGeneration.cs b/src/SourceGenerators/Uno.UI.SourceGenerators/XamlGenerator/XamlCodeGeneration.cs
index f6e718155eb4..8c5cfcff7cce 100644
--- a/src/SourceGenerators/Uno.UI.SourceGenerators/XamlGenerator/XamlCodeGeneration.cs
+++ b/src/SourceGenerators/Uno.UI.SourceGenerators/XamlGenerator/XamlCodeGeneration.cs
@@ -495,6 +495,13 @@ private string GenerateGlobalResources(IEnumerable<XamlFileDefinition> files, Xa
 			writer.AppendLineInvariant("using {0};", _defaultNamespace);
 			writer.AppendLineInvariant("");
 
+			// If a failure happens here, this means that the _isWasm was not properly set as the DefineConstants msbuild property
+			// was not populated. This can happen when the property is set through a target with the "CreateProperty" task, and the
+			// Uno.SourceGeneration tasks do not execute this task properly.
+			writer.AppendLineInvariant("#if __WASM__");
+			writer.AppendLineInvariant(_isWasm ? "" : "#error invalid internal source generator state. The __WASM__ DefineConstant was not propagated properly.");
+			writer.AppendLineInvariant("#endif");
+
 			using (writer.BlockInvariant("namespace {0}", _defaultNamespace))
 			{
 				writer.AppendLineInvariant("/// <summary>");
diff --git a/src/Uno.UI.Runtime.Skia.Gtk/buildTransitive/Uno.UI.Runtime.Skia.Gtk.targets b/src/Uno.UI.Runtime.Skia.Gtk/buildTransitive/Uno.UI.Runtime.Skia.Gtk.targets
index 41a43c45e958..ff1054fdcf53 100644
--- a/src/Uno.UI.Runtime.Skia.Gtk/buildTransitive/Uno.UI.Runtime.Skia.Gtk.targets
+++ b/src/Uno.UI.Runtime.Skia.Gtk/buildTransitive/Uno.UI.Runtime.Skia.Gtk.targets
@@ -5,7 +5,7 @@
   </PropertyGroup>
   
   <Target Name="_UnoSkiaGtkFeatureDefines"
-		  BeforeTargets="BeforeCompile">
+		  BeforeTargets="PrepareForBuild">
 
 	<PropertyGroup>
 	  <UnoDefineConstants>$(UnoDefineConstants);UNO_REFERENCE_API;HAS_UNO_SKIA;HAS_UNO_SKIA_GTK</UnoDefineConstants>
diff --git a/src/Uno.UI.Runtime.Skia.Tizen/buildTransitive/Uno.UI.Runtime.Skia.Tizen.targets b/src/Uno.UI.Runtime.Skia.Tizen/buildTransitive/Uno.UI.Runtime.Skia.Tizen.targets
index d2b5d40d14bf..638bb7c4f74e 100644
--- a/src/Uno.UI.Runtime.Skia.Tizen/buildTransitive/Uno.UI.Runtime.Skia.Tizen.targets
+++ b/src/Uno.UI.Runtime.Skia.Tizen/buildTransitive/Uno.UI.Runtime.Skia.Tizen.targets
@@ -5,7 +5,7 @@
   </PropertyGroup>
   
   <Target Name="_UnoSkiaTizenFeatureDefines"
-		  BeforeTargets="BeforeCompile">
+		  BeforeTargets="PrepareForBuild">
 
 	<PropertyGroup>
 	  <UnoDefineConstants>$(UnoDefineConstants);UNO_REFERENCE_API;HAS_UNO_SKIA;HAS_UNO_SKIA_TIZEN</UnoDefineConstants>
diff --git a/src/Uno.UI.Runtime.Skia.Wpf/buildTransitive/Uno.UI.Runtime.Skia.Wpf.targets b/src/Uno.UI.Runtime.Skia.Wpf/buildTransitive/Uno.UI.Runtime.Skia.Wpf.targets
index 9eed6c3aabee..bc2879ee8c0d 100644
--- a/src/Uno.UI.Runtime.Skia.Wpf/buildTransitive/Uno.UI.Runtime.Skia.Wpf.targets
+++ b/src/Uno.UI.Runtime.Skia.Wpf/buildTransitive/Uno.UI.Runtime.Skia.Wpf.targets
@@ -2,7 +2,7 @@
 <Project xmlns="http://schemas.microsoft.com/developer/msbuild/2003">
   
   <Target Name="_UnoSkiaWpfFeatureDefines"
-		  BeforeTargets="BeforeCompile">
+		  BeforeTargets="PrepareForBuild">
 
 	<PropertyGroup>
 	  <UnoDefineConstants>$(UnoDefineConstants);UNO_REFERENCE_API;HAS_UNO_SKIA;HAS_UNO_SKIA_WPF</UnoDefineConstants>
diff --git a/src/Uno.UI.Runtime.WebAssembly/buildTransitive/Uno.UI.Runtime.WebAssembly.targets b/src/Uno.UI.Runtime.WebAssembly/buildTransitive/Uno.UI.Runtime.WebAssembly.targets
index 8f582791b035..c34be8c031a0 100644
--- a/src/Uno.UI.Runtime.WebAssembly/buildTransitive/Uno.UI.Runtime.WebAssembly.targets
+++ b/src/Uno.UI.Runtime.WebAssembly/buildTransitive/Uno.UI.Runtime.WebAssembly.targets
@@ -5,7 +5,7 @@
   </PropertyGroup>
 
   <Target Name="_UnoSkiaWasmFeatureDefines"
-		  BeforeTargets="BeforeCompile">
+		  BeforeTargets="PrepareForBuild">
 
 	<PropertyGroup>
 	  <UnoDefineConstants>$(UnoDefineConstants);UNO_REFERENCE_API;HAS_UNO_WASM;__WASM__</UnoDefineConstants>