Index: src/OFApplication.m
==================================================================
--- src/OFApplication.m
+++ src/OFApplication.m
@@ -123,17 +123,14 @@
 	int wargc, si = 0;
 #endif
 
 	[[OFLocalization alloc] init];
 
-	if ([cls isSubclassOfClass: [OFApplication class]]) {
-		fprintf(stderr, "FATAL ERROR:\n  Class %s is a subclass of "
-		    "class OFApplication, but class\n  %s was specified as "
-		    "application delegate!\n  Most likely, you wanted to "
-		    "subclass OFObject instead or specified\n  the wrong class "
-		    "with OF_APPLICATION_DELEGATE().\n",
-		    class_getName(cls), class_getName(cls));
+	if (![cls conformsToProtocol: @protocol(OFApplicationDelegate)]) {
+		fprintf(stderr, "FATAL ERROR:\n  Class %s does not conform to "
+		    "protocol OFApplicationDelegate,\n  but was specified via "
+		    "OF_APPLICATION_DELEGATE()!\n", class_getName(cls));
 		exit(1);
 	}
 
 	app = [[OFApplication alloc] of_init];
 

Index: utils/ofhash/OFHash.m
==================================================================
--- utils/ofhash/OFHash.m
+++ utils/ofhash/OFHash.m
@@ -31,11 +31,11 @@
 #import "OFSandbox.h"
 
 #import "OFOpenItemFailedException.h"
 #import "OFReadFailedException.h"
 
-@interface OFHash: OFObject
+@interface OFHash: OFObject <OFApplicationDelegate>
 @end
 
 OF_APPLICATION_DELEGATE(OFHash)
 
 static void

Index: utils/ofhttp/OFHTTP.m
==================================================================
--- utils/ofhttp/OFHTTP.m
+++ utils/ofhttp/OFHTTP.m
@@ -50,11 +50,11 @@
 
 #define GIBIBYTE (1024 * 1024 * 1024)
 #define MEBIBYTE (1024 * 1024)
 #define KIBIBYTE (1024)
 
-@interface OFHTTP: OFObject <OFHTTPClientDelegate>
+@interface OFHTTP: OFObject <OFApplicationDelegate, OFHTTPClientDelegate>
 {
 	OFArray OF_GENERIC(OFString *) *_URLs;
 	size_t _URLIndex;
 	int _errorCode;
 	OFString *_outputPath, *_currentFileName;

Index: utils/ofzip/OFZIP.h
==================================================================
--- utils/ofzip/OFZIP.h
+++ utils/ofzip/OFZIP.h
@@ -24,11 +24,11 @@
 #endif
 #ifndef S_IRWXO
 # define S_IRWXO 0
 #endif
 
-@interface OFZIP: OFObject
+@interface OFZIP: OFObject <OFApplicationDelegate>
 {
 	int8_t _overwrite;
 @public
 	int8_t _outputLevel;
 	OFString *_archivePath;