diff --git a/Source/Core/Data/PK3Reader.cs b/Source/Core/Data/PK3Reader.cs
index 329ea67..18db05f 100644
--- a/Source/Core/Data/PK3Reader.cs
+++ b/Source/Core/Data/PK3Reader.cs
@@ -37,6 +37,7 @@ namespace CodeImp.DoomBuilder.Data
 		private readonly ArchiveType archivetype; //mxd
 		private readonly Dictionary<string, byte[]> sevenzipentries; //mxd
 		private bool bathmode = true; //mxd
+		private FileStream filestream;
 
 		#endregion
 
@@ -51,6 +52,9 @@ namespace CodeImp.DoomBuilder.Data
 		// Constructor
 		public PK3Reader(DataLocation dl) : base(dl)
 		{
+			FileAccess access = FileAccess.Read;
+			FileShare share = FileShare.ReadWrite;
+
 			General.WriteLogLine("Opening " + Path.GetExtension(location.location).ToUpper().Replace(".", "") + " resource '" + location.location + "'");
 
 			if(!File.Exists(location.location))
@@ -59,8 +63,11 @@ namespace CodeImp.DoomBuilder.Data
 			// Make list of all files
 			List<DirectoryFileEntry> fileentries = new List<DirectoryFileEntry>();
 
+			// Take the detour with a FileStream because SharpCompress doesn't directly support opening files as read-only
+			filestream = File.Open(location.location, FileMode.OpenOrCreate, access, share);
+
 			// Create archive
-			archive = ArchiveFactory.Open(location.location, Options.KeepStreamsOpen);
+			archive = ArchiveFactory.Open(filestream);
 			archivetype = archive.Type;
 
 			// Random access of 7z archives works TERRIBLY slow in SharpCompress
@@ -92,6 +99,9 @@ namespace CodeImp.DoomBuilder.Data
 			archive.Dispose();
 			archive = null;
 
+			filestream.Dispose();
+			filestream = null;
+
 			// Make files list
 			files = new DirectoryFilesList(fileentries);
 			
@@ -117,6 +127,12 @@ namespace CodeImp.DoomBuilder.Data
 					archive = null;
 				}
 
+				if (filestream != null)
+				{
+					filestream.Dispose();
+					filestream = null;
+				}
+
 				// Done
 				base.Dispose();
 			}
@@ -129,12 +145,25 @@ namespace CodeImp.DoomBuilder.Data
 
 			if(enable && archive == null)
 			{
-				archive = ArchiveFactory.Open(location.location);
+				FileAccess access = FileAccess.Read;
+				FileShare share = FileShare.ReadWrite;
+
+				// The file might have vanished in the meantime
+				if (!File.Exists(location.location))
+					throw new FileNotFoundException("Could not find the file \"" + location.location + "\"", location.location);
+				
+				// Take the detour with a FileStream because SharpCompress doesn't directly support opening files as read-only
+				filestream = File.Open(location.location, FileMode.OpenOrCreate, access, share);
+
+				archive = ArchiveFactory.Open(filestream);
 			} 
 			else if(!enable && !bathmode && archive != null)
 			{
 				archive.Dispose();
 				archive = null;
+
+				filestream.Dispose();
+				filestream = null;
 			}
 		}