diff --git a/src/Nazara/Shader/SpirvAstVisitor.cpp b/src/Nazara/Shader/SpirvAstVisitor.cpp
index d66f76170..6cf45cee7 100644
--- a/src/Nazara/Shader/SpirvAstVisitor.cpp
+++ b/src/Nazara/Shader/SpirvAstVisitor.cpp
@@ -15,6 +15,8 @@ namespace Nz
 	UInt32 SpirvAstVisitor::EvaluateExpression(const ShaderNodes::ExpressionPtr& expr)
 	{
 		Visit(expr);
+
+		assert(m_resultIds.size() == 1);
 		return PopResultId();
 	}