diff --git a/spine-unity/Assets/Spine/Editor/spine-unity/Editor/Utility/AssetUtility.cs b/spine-unity/Assets/Spine/Editor/spine-unity/Editor/Utility/AssetUtility.cs
index 98afec85a..fe8c5c87f 100644
--- a/spine-unity/Assets/Spine/Editor/spine-unity/Editor/Utility/AssetUtility.cs
+++ b/spine-unity/Assets/Spine/Editor/spine-unity/Editor/Utility/AssetUtility.cs
@@ -658,7 +658,6 @@ namespace Spine.Unity.Editor {
 				foreach (Material m in atlasAsset.materials)
 					vestigialMaterials.Add(m);
 			}
-
 			protectFromStackGarbageCollection.Add(atlasAsset);
 			atlasAsset.atlasFile = atlasText;
 
@@ -669,6 +668,7 @@ namespace Spine.Unity.Editor {
 				foreach (AtlasPage page in atlas.Pages)
 					pageFiles.Add(page.name);
 			}
+			bool atlasHasCustomMaterials = HasCustomMaterialsAssigned(vestigialMaterials, primaryName, pageFiles);
 
 			List<Material> populatingMaterials = new List<Material>(pageFiles.Count);
 			string materialDirectory = GetMaterialDirectory(assetPath, vestigialMaterials);
@@ -685,12 +685,8 @@ namespace Spine.Unity.Editor {
 				}
 
 				string pageName = Path.GetFileNameWithoutExtension(pageFiles[i]);
-
-				//because this looks silly
-				if (pageName == primaryName && pageFiles.Count == 1)
-					pageName = "Material";
-
-				string materialPath = materialDirectory + "/" + primaryName + "_" + pageName + ".mat";
+				string materialFileName = GetPageMaterialName(primaryName, pageName, pageFiles) + ".mat";
+				string materialPath = materialDirectory + "/" + materialFileName;
 				Material material = (Material)AssetDatabase.LoadAssetAtPath(materialPath, typeof(Material));
 				if (material == null) {
 					Shader defaultShader = GetDefaultShader();
@@ -714,10 +710,11 @@ namespace Spine.Unity.Editor {
 				}
 			}
 
-			atlasAsset.materials = populatingMaterials.ToArray();
-
-			for (int i = 0; i < vestigialMaterials.Count; i++)
-				AssetDatabase.DeleteAsset(AssetDatabase.GetAssetPath(vestigialMaterials[i]));
+			if (!atlasHasCustomMaterials) {
+				atlasAsset.materials = populatingMaterials.ToArray();
+				for (int i = 0; i < vestigialMaterials.Count; i++)
+					AssetDatabase.DeleteAsset(AssetDatabase.GetAssetPath(vestigialMaterials[i]));
+			}
 
 			if (AssetDatabase.GetAssetPath(atlasAsset) == "")
 				AssetDatabase.CreateAsset(atlasAsset, atlasPath);
@@ -727,9 +724,14 @@ namespace Spine.Unity.Editor {
 			EditorUtility.SetDirty(atlasAsset);
 			AssetDatabase.SaveAssets();
 
-			if (pageFiles.Count != atlasAsset.materials.Length)
-				Debug.LogWarning(string.Format("{0} :: Not all atlas pages were imported. If you rename your image files, please make sure you also edit the filenames specified in the atlas file.", atlasAsset.name), atlasAsset);
-			else
+			if (pageFiles.Count != atlasAsset.materials.Length) {
+				if (atlasHasCustomMaterials)
+					Debug.LogWarning(string.Format("{0} :: Found custom materials at atlas asset, but atlas page count " +
+						"changed. Please update the Materials list accordingly.", atlasAsset.name), atlasAsset);
+				else
+					Debug.LogWarning(string.Format("{0} :: Not all atlas pages were imported. If you rename your image " +
+						"files, please make sure you also edit the filenames specified in the atlas file.", atlasAsset.name), atlasAsset);
+			} else
 				Debug.Log(string.Format("{0} :: Imported with {1} material", atlasAsset.name, atlasAsset.materials.Length), atlasAsset);
 
 			// Iterate regions and bake marked.
@@ -766,6 +768,15 @@ namespace Spine.Unity.Editor {
 			return loadedAtlas != null ? loadedAtlas : atlasAsset;
 		}
 
+		static bool HasCustomMaterialsAssigned (List<Material> vestigialMaterials, string primaryName, List<string> pageFiles) {
+			if (pageFiles.Count == 0 || vestigialMaterials.Count == 0)
+				return false;
+
+			string firstPageName = Path.GetFileNameWithoutExtension(pageFiles[0]);
+			string defaultMaterialName = GetPageMaterialName(primaryName, firstPageName, pageFiles);
+			return vestigialMaterials[0].name != defaultMaterialName;
+		}
+
 		public static Shader GetDefaultShader () {
 			Shader shader = Shader.Find(SpineEditorUtilities.Preferences.DefaultShader);
 			if (shader == null) shader = Shader.Find("Spine/Skeleton");
@@ -928,6 +939,13 @@ namespace Spine.Unity.Editor {
 			return (AtlasAssetBase)AssetDatabase.LoadAssetAtPath(atlasPath, typeof(AtlasAssetBase));
 		}
 
+		static string GetPageMaterialName (string primaryName, string pageName, List<string> pageFiles) {
+			// use skeleton_Material.mat instead of skeleton_skeleton.mat if we have just a single atlas page
+			if (pageName == primaryName && pageFiles.Count == 1)
+				pageName = "Material";
+			return primaryName + "_" + pageName;
+		}
+
 		static string GetMaterialDirectory (string assetPath, List<Material> previousMaterials) {
 			if (previousMaterials.Count > 0 && previousMaterials[0] != null) {
 				string materialPath = AssetDatabase.GetAssetPath(previousMaterials[0]);
diff --git a/spine-unity/Assets/Spine/package.json b/spine-unity/Assets/Spine/package.json
index 6ee911457..44a11044c 100644
--- a/spine-unity/Assets/Spine/package.json
+++ b/spine-unity/Assets/Spine/package.json
@@ -2,7 +2,7 @@
 	"name": "com.esotericsoftware.spine.spine-unity",
 	"displayName": "spine-unity Runtime",
 	"description": "This plugin provides the spine-unity runtime core.",
-	"version": "4.2.99",
+	"version": "4.2.100",
 	"unity": "2018.3",
 	"author": {
 		"name": "Esoteric Software",