diff --git a/jni/NativeFormats/zlibrary/core/src/drm/FileEncryptionInfo.cpp b/jni/NativeFormats/zlibrary/core/src/drm/FileEncryptionInfo.cpp
index 34180aee0..58af4ff37 100644
--- a/jni/NativeFormats/zlibrary/core/src/drm/FileEncryptionInfo.cpp
+++ b/jni/NativeFormats/zlibrary/core/src/drm/FileEncryptionInfo.cpp
@@ -21,7 +21,6 @@
 
 #include "FileEncryptionInfo.h"
 
-const std::string EncryptionMethod::NONE = "none";
 const std::string EncryptionMethod::UNSUPPORTED = "unsupported";
 const std::string EncryptionMethod::EMBEDDING = "embedding";
 const std::string EncryptionMethod::MARLIN = "marlin";
diff --git a/jni/NativeFormats/zlibrary/core/src/drm/FileEncryptionInfo.h b/jni/NativeFormats/zlibrary/core/src/drm/FileEncryptionInfo.h
index 2c58f9e11..88c3f135d 100644
--- a/jni/NativeFormats/zlibrary/core/src/drm/FileEncryptionInfo.h
+++ b/jni/NativeFormats/zlibrary/core/src/drm/FileEncryptionInfo.h
@@ -29,7 +29,6 @@
 class EncryptionMethod {
 
 public:
-	static const std::string NONE;
 	static const std::string UNSUPPORTED;
 	static const std::string EMBEDDING;
 	static const std::string MARLIN;
diff --git a/src/org/geometerplus/fbreader/fbreader/FBReaderApp.java b/src/org/geometerplus/fbreader/fbreader/FBReaderApp.java
index b199f44ac..8e9d7f508 100644
--- a/src/org/geometerplus/fbreader/fbreader/FBReaderApp.java
+++ b/src/org/geometerplus/fbreader/fbreader/FBReaderApp.java
@@ -284,7 +284,7 @@ public final class FBReaderApp extends ZLApplication {
 
 		try {
 			for (FileEncryptionInfo info : book.getPlugin().readEncryptionInfos(book)) {
-				if (!EncryptionMethod.NONE.equals(info.Method)) {
+				if (info != null && !EncryptionMethod.isSupported(info.Method)) {
 					showErrorMessage("unsupportedEncryptionMethod", book.File.getPath());
 					break;
 				}
diff --git a/src/org/geometerplus/zlibrary/core/drm/EncryptionMethod.java b/src/org/geometerplus/zlibrary/core/drm/EncryptionMethod.java
index 8bf80e3b5..3e83b3b6a 100644
--- a/src/org/geometerplus/zlibrary/core/drm/EncryptionMethod.java
+++ b/src/org/geometerplus/zlibrary/core/drm/EncryptionMethod.java
@@ -19,9 +19,12 @@
 
 package org.geometerplus.zlibrary.core.drm;
 
-public interface EncryptionMethod {
-	String NONE = "none";
-	String UNSUPPORTED = "unsupported";
-	String EMBEDDING = "embedding";
-	String MARLIN = "marlin";
+public abstract class EncryptionMethod {
+	public static final String UNSUPPORTED = "unsupported";
+	public static final String EMBEDDING = "embedding";
+	public static final String MARLIN = "marlin";
+
+	public static boolean isSupported(String method) {
+		return false;
+	}
 }