diff --git a/include/IVideoDriver.h b/include/IVideoDriver.h
index aef4820c..9c4d84c4 100644
--- a/include/IVideoDriver.h
+++ b/include/IVideoDriver.h
@@ -1343,7 +1343,7 @@ 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 cd02b3c5..069b2cc2 100644
--- a/source/Irrlicht/CNullDriver.cpp
+++ b/source/Irrlicht/CNullDriver.cpp
@@ -2093,10 +2093,10 @@ 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 711a49ac..33c96e60 100644
--- a/source/Irrlicht/CNullDriver.h
+++ b/source/Irrlicht/CNullDriver.h
@@ -613,7 +613,7 @@ namespace video
 		virtual bool writeImageToFile(IImage* image, io::IWriteFile * file, u32 param = 0) IRR_OVERRIDE;
 
 		//! Sets the name of a material renderer.
-		virtual void setMaterialRendererName(s32 idx, const char* name) IRR_OVERRIDE;
+		virtual void setMaterialRendererName(u32 idx, const char* name) IRR_OVERRIDE;
 
 		//! Swap the material renderers used for certain id's
 		virtual void swapMaterialRenderers(u32 idx1, u32 idx2, bool swapNames) IRR_OVERRIDE;