diff --git a/include/IVideoDriver.h b/include/IVideoDriver.h
index b220e5e6..ed4e6fa5 100644
--- a/include/IVideoDriver.h
+++ b/include/IVideoDriver.h
@@ -1279,7 +1279,7 @@ namespace video
 		E_MATERIAL_TYPE enum or a value which was returned by
 		addMaterialRenderer().
 		\param name: New name of the material renderer. */
-		virtual void setMaterialRendererName(s32 idx, const c8* name) =0;
+		virtual void setMaterialRendererName(u32 idx, const c8* name) =0;
 
 		//! Swap the material renderers used for certain id's
 		/** Swap the IMaterialRenderers responsible for rendering specific
diff --git a/source/Irrlicht/CNullDriver.cpp b/source/Irrlicht/CNullDriver.cpp
index 2cbd47cd..21e143a4 100644
--- a/source/Irrlicht/CNullDriver.cpp
+++ b/source/Irrlicht/CNullDriver.cpp
@@ -1824,10 +1824,10 @@ s32 CNullDriver::addMaterialRenderer(IMaterialRenderer* renderer, const char* na
 
 
 //! Sets the name of a material renderer.
-void CNullDriver::setMaterialRendererName(s32 idx, const char* name)
+void CNullDriver::setMaterialRendererName(u32 idx, const char* name)
 {
-	if (idx < s32(sizeof(sBuiltInMaterialTypeNames) / sizeof(char*))-1 ||
-		idx >= (s32)MaterialRenderers.size())
+	if (idx < (sizeof(sBuiltInMaterialTypeNames) / sizeof(char*))-1 ||
+		idx >= MaterialRenderers.size())
 		return;
 
 	MaterialRenderers[idx].Name = name;
diff --git a/source/Irrlicht/CNullDriver.h b/source/Irrlicht/CNullDriver.h
index e6cdce66..625ff1a6 100644
--- a/source/Irrlicht/CNullDriver.h
+++ b/source/Irrlicht/CNullDriver.h
@@ -585,7 +585,7 @@ namespace video
 		bool writeImageToFile(IImage* image, io::IWriteFile * file, u32 param = 0) override;
 
 		//! Sets the name of a material renderer.
-		void setMaterialRendererName(s32 idx, const char* name) override;
+		void setMaterialRendererName(u32 idx, const char* name) override;
 
 		//! Swap the material renderers used for certain id's
 		void swapMaterialRenderers(u32 idx1, u32 idx2, bool swapNames) override;