diff --git a/code/AssbinLoader.cpp b/code/AssbinLoader.cpp
index 7adb8db6f..acba8b3dd 100644
--- a/code/AssbinLoader.cpp
+++ b/code/AssbinLoader.cpp
@@ -708,7 +708,7 @@ void AssbinImporter::InternReadFile( const std::string& pFile, aiScene* pScene,
 
         unsigned char * uncompressedData = new unsigned char[ uncompressedSize ];
 
-        int res = uncompress( uncompressedData, &uncompressedSize, compressedData, len );
+        int res = uncompress( uncompressedData, &uncompressedSize, compressedData, (uLong) len );
         if(res != Z_OK)
         {
             delete [] uncompressedData;
diff --git a/code/FBXConverter.cpp b/code/FBXConverter.cpp
index c556d3bba..a61ae4006 100644
--- a/code/FBXConverter.cpp
+++ b/code/FBXConverter.cpp
@@ -964,7 +964,7 @@ namespace Assimp {
             {
                 if (indices[i] < 0) epcount++;
             }
-            unsigned int pcount = indices.size();
+            unsigned int pcount = static_cast<unsigned int>( indices.size() );
             unsigned int scount = out_mesh->mNumFaces = pcount - epcount;
 
             aiFace* fac = out_mesh->mFaces = new aiFace[scount]();
diff --git a/code/SMDLoader.cpp b/code/SMDLoader.cpp
index 00d92e0b4..4288bf9c3 100644
--- a/code/SMDLoader.cpp
+++ b/code/SMDLoader.cpp
@@ -486,7 +486,7 @@ void SMDImporter::CreateOutputAnimations(const std::string &pFile, IOSystem* pIO
     if (bLoadAnimationList) {
         GetAnimationFileList(pFile, pIOHandler, animFileList);
     }
-    int animCount = animFileList.size() + 1;
+    int animCount = static_cast<int>( animFileList.size() + 1u );
     pScene->mNumAnimations = 1;
     pScene->mAnimations = new aiAnimation*[animCount];
     memset(pScene->mAnimations, 0, sizeof(aiAnimation*)*animCount);
@@ -510,7 +510,7 @@ void SMDImporter::CreateOutputAnimation(int index, const std::string &name) {
         anim->mName.Set(name.c_str());
     }
     anim->mDuration = dLengthOfAnim;
-    anim->mNumChannels = asBones.size();
+    anim->mNumChannels = static_cast<unsigned int>( asBones.size() );
     anim->mTicksPerSecond = 25.0; // FIXME: is this correct?
 
     aiNodeAnim** pp = anim->mChannels = new aiNodeAnim*[anim->mNumChannels];
diff --git a/test/unit/utSTLImportExport.cpp b/test/unit/utSTLImportExport.cpp
index b5518de23..0f90aacf9 100644
--- a/test/unit/utSTLImportExport.cpp
+++ b/test/unit/utSTLImportExport.cpp
@@ -152,10 +152,10 @@ TEST_F(utSTLImporterExporter, test_export_pointclouds) {
 
     auto pMesh = scene.mMeshes[0];
 
-    long numValidPoints = points.size();
+    size_t numValidPoints = points.size();
 
     pMesh->mVertices = new aiVector3D[numValidPoints];
-    pMesh->mNumVertices = numValidPoints;
+    pMesh->mNumVertices = static_cast<unsigned int>( numValidPoints );
 
     int i = 0;
     for (XYZ &p : points) {
diff --git a/tools/assimp_view/SceneAnimator.cpp b/tools/assimp_view/SceneAnimator.cpp
index c2ebeacb3..86fe46a9c 100644
--- a/tools/assimp_view/SceneAnimator.cpp
+++ b/tools/assimp_view/SceneAnimator.cpp
@@ -90,7 +90,7 @@ void SceneAnimator::SetAnimIndex( size_t pAnimIndex) {
     delete mAnimEvaluator;  mAnimEvaluator = nullptr;
     mNodesByName.clear();
 
-    mCurrentAnimIndex = pAnimIndex;
+    mCurrentAnimIndex = static_cast<int>( pAnimIndex );
 
     // create the internal node tree. Do this even in case of invalid animation index
     // so that the transformation matrices are properly set up to mimic the current scene