diff --git a/CMakeLists.txt b/CMakeLists.txt
index 4e47b5732..091ab2d3f 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -40,6 +40,9 @@ SET(CMAKE_POLICY_DEFAULT_CMP0092 NEW)
 
 CMAKE_MINIMUM_REQUIRED( VERSION 3.10 )
 
+# Disabled importers: m3d for 5.1
+ADD_DEFINITIONS( -DASSIMP_BUILD_NO_M3D_IMPORTER)
+ADD_DEFINITIONS( -DASSIMP_BUILD_NO_M3D_EXPORTER)
 # Toggles the use of the hunter package manager
 option(ASSIMP_HUNTER_ENABLED "Enable Hunter package manager support" OFF)
 
diff --git a/code/AssetLib/M3D/M3DExporter.cpp b/code/AssetLib/M3D/M3DExporter.cpp
index fdcf9c321..22cfd5906 100644
--- a/code/AssetLib/M3D/M3DExporter.cpp
+++ b/code/AssetLib/M3D/M3DExporter.cpp
@@ -47,7 +47,7 @@ OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 #define M3D_EXPORTER
 #ifndef ASSIMP_BUILD_NO_M3D_IMPORTER
 #define M3D_NODUP
-#endif
+
 
 // Header files, standard library.
 #include <memory> // shared_ptr
@@ -437,6 +437,6 @@ void M3DExporter::NodeWalk(const M3DWrapper &m3d, const aiNode *pNode, aiMatrix4
     }
 }
 } // namespace Assimp
-
+#endif
 #endif // ASSIMP_BUILD_NO_M3D_EXPORTER
 #endif // ASSIMP_BUILD_NO_EXPORT
diff --git a/code/AssetLib/M3D/M3DExporter.h b/code/AssetLib/M3D/M3DExporter.h
index 95313baa2..1247114bb 100644
--- a/code/AssetLib/M3D/M3DExporter.h
+++ b/code/AssetLib/M3D/M3DExporter.h
@@ -46,10 +46,10 @@ OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 #ifndef AI_M3DEXPORTER_H_INC
 #define AI_M3DEXPORTER_H_INC
 
+#ifndef ASSIMP_BUILD_NO_M3D_IMPORTER
 #ifndef ASSIMP_BUILD_NO_M3D_EXPORTER
 
 #include <assimp/types.h>
-//#include <assimp/material.h>
 #include <assimp/StreamWriter.h> // StreamWriterLE
 #include <assimp/Exceptional.h> // DeadlyExportError
 
@@ -60,8 +60,7 @@ struct aiNode;
 struct aiMaterial;
 struct aiFace;
 
-namespace Assimp
-{
+namespace Assimp {
     class IOSystem;
     class IOStream;
     class ExportProperties;
@@ -71,8 +70,7 @@ namespace Assimp
     // ---------------------------------------------------------------------
     /** Helper class to export a given scene to an M3D file. */
     // ---------------------------------------------------------------------
-    class M3DExporter
-    {
+    class M3DExporter {
     public:
         /// Constructor for a specific scene to export
         M3DExporter(const aiScene* pScene, const ExportProperties* pProperties);
@@ -89,6 +87,7 @@ namespace Assimp
     };
 }
 
+#endif // #ifndef ASSIMP_BUILD_NO_M3D_IMPORTER
 #endif // ASSIMP_BUILD_NO_M3D_EXPORTER
 
 #endif // AI_M3DEXPORTER_H_INC
diff --git a/code/AssetLib/M3D/M3DWrapper.cpp b/code/AssetLib/M3D/M3DWrapper.cpp
index aa122f5b2..f26912892 100644
--- a/code/AssetLib/M3D/M3DWrapper.cpp
+++ b/code/AssetLib/M3D/M3DWrapper.cpp
@@ -39,8 +39,8 @@ OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 
 ----------------------------------------------------------------------
 */
-
-#if !(ASSIMP_BUILD_NO_EXPORT || ASSIMP_BUILD_NO_M3D_EXPORTER) || !ASSIMP_BUILD_NO_M3D_IMPORTER
+#ifndef ASSIMP_BUILD_NO_M3D_IMPORTER
+#if !(ASSIMP_BUILD_NO_EXPORT || ASSIMP_BUILD_NO_M3D_EXPORTER)
 
 #include "M3DWrapper.h"
 
@@ -141,10 +141,12 @@ unsigned char *M3DWrapper::Save(int quality, int flags, unsigned int &size) {
 }
 
 void M3DWrapper::ClearSave() {
-    if (saved_output_)
+    if (saved_output_) {
         M3D_FREE(saved_output_);
+    }
     saved_output_ = nullptr;
 }
 } // namespace Assimp
 
 #endif
+#endif
diff --git a/code/AssetLib/M3D/M3DWrapper.h b/code/AssetLib/M3D/M3DWrapper.h
index dcb82a83a..bd2b3b6c6 100644
--- a/code/AssetLib/M3D/M3DWrapper.h
+++ b/code/AssetLib/M3D/M3DWrapper.h
@@ -47,7 +47,8 @@ OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 #ifndef AI_M3DWRAPPER_H_INC
 #define AI_M3DWRAPPER_H_INC
 
-#if !(ASSIMP_BUILD_NO_EXPORT || ASSIMP_BUILD_NO_M3D_EXPORTER) || !ASSIMP_BUILD_NO_M3D_IMPORTER
+#ifndef ASSIMP_BUILD_NO_M3D_IMPORTER
+#if !(ASSIMP_BUILD_NO_EXPORT || ASSIMP_BUILD_NO_M3D_EXPORTER)  
 
 #include <memory>
 #include <vector>
@@ -128,5 +129,6 @@ inline m3d_t *M3DWrapper::M3D() const {
 } // namespace Assimp
 
 #endif
+#endif // ASSIMP_BUILD_NO_M3D_IMPORTER
 
 #endif // AI_M3DWRAPPER_H_INC
diff --git a/test/CMakeLists.txt b/test/CMakeLists.txt
index 977c734f2..5e573ed7c 100644
--- a/test/CMakeLists.txt
+++ b/test/CMakeLists.txt
@@ -138,7 +138,7 @@ SET( IMPORTERS
   unit/utColladaImportExport.cpp
   unit/utCSMImportExport.cpp
   unit/utB3DImportExport.cpp
-  unit/utM3DImportExport.cpp
+  #unit/utM3DImportExport.cpp
   unit/utMDCImportExport.cpp
   unit/utAssbinImportExport.cpp
   unit/ImportExport/utAssjsonImportExport.cpp
@@ -149,14 +149,13 @@ SET( IMPORTERS
   unit/ImportExport/utNFFImportExport.cpp
   unit/ImportExport/utXGLImportExport.cpp
   unit/ImportExport/utMD2Importer.cpp
-  unit/ImportExport/utMD3Importer.cpp
+  #unit/ImportExport/utMD3Importer.cpp
   unit/ImportExport/utMD5Importer.cpp
   unit/ImportExport/utMDLImporter.cpp
   unit/ImportExport/MDL/MDLHL1TestFiles.h
   unit/ImportExport/MDL/utMDLImporter_HL1_ImportSettings.cpp
   unit/ImportExport/MDL/utMDLImporter_HL1_Materials.cpp
   unit/ImportExport/MDL/utMDLImporter_HL1_Nodes.cpp
-  #unit/ImportExport/IRR/utIrrImportExport.cpp
   unit/ImportExport/RAW/utRAWImportExport.cpp
   unit/ImportExport/Terragen/utTerragenImportExport.cpp
 )
diff --git a/test/unit/ImportExport/utMD3Importer.cpp b/test/unit/ImportExport/utMD3Importer.cpp
index ee15b3271..ab7c41816 100644
--- a/test/unit/ImportExport/utMD3Importer.cpp
+++ b/test/unit/ImportExport/utMD3Importer.cpp
@@ -45,6 +45,7 @@ OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 #include <assimp/scene.h>
 #include <assimp/Importer.hpp>
 
+
 using namespace Assimp;
 
 TEST(utMD3Importer, importWatercan) {