Index: src/OFDNSResolver.h
==================================================================
--- src/OFDNSResolver.h
+++ src/OFDNSResolver.h
@@ -30,10 +30,11 @@
 @class OFDNSResolverSettings;
 @class OFDate;
 @class OFDictionary OF_GENERIC(KeyType, ObjectType);
 @class OFMutableDictionary OF_GENERIC(KeyType, ObjectType);
 @class OFNumber;
+@class OFPair OF_GENERIC(FirstType, SecondType);
 @class OFTCPSocket;
 @class OFUDPSocket;
 
 /**
  * @enum OFDNSResolverErrorCode OFDNSResolver.h ObjFW/OFDNSResolver.h
@@ -132,10 +133,12 @@
 	char _buffer[OFDNSResolverBufferLength];
 	OFMutableDictionary OF_GENERIC(OFNumber *, OFDNSResolverContext *)
 	    *_queries;
 	OFMutableDictionary OF_GENERIC(OFTCPSocket *, OFDNSResolverContext *)
 	    *_TCPQueries;
+	OFMutableDictionary OF_GENERIC(OFDNSQuery *,
+	    OFPair OF_GENERIC(OFDate *, OFDNSResponse *) *) *_cache;
 }
 
 /**
  * @brief A dictionary of static hosts.
  *

Index: src/OFDNSResolver.m
==================================================================
--- src/OFDNSResolver.m
+++ src/OFDNSResolver.m
@@ -464,10 +464,24 @@
 
 	[ret makeImmutable];
 
 	return ret;
 }
+
+static bool
+containsExpiredRecord(OFDNSResponseRecords responseRecords, uint32_t age)
+{
+	OFEnumerator *enumerator = [responseRecords objectEnumerator];
+	OFArray OF_GENERIC(OFDNSResourceRecord *) *records;
+
+	while ((records = [enumerator nextObject]) != nil)
+		for (OFDNSResourceRecord *record in records)
+			if (record.TTL < age)
+				return true;
+
+	return false;
+}
 
 @implementation OFDNSResolverContext
 - (instancetype)initWithQuery: (OFDNSQuery *)query
 			   ID: (OFNumber *)ID
 		     settings: (OFDNSResolverSettings *)settings
@@ -576,10 +590,11 @@
 
 	@try {
 		_settings = [[OFDNSResolverSettings alloc] init];
 		_queries = [[OFMutableDictionary alloc] init];
 		_TCPQueries = [[OFMutableDictionary alloc] init];
+		_cache = [[OFMutableDictionary alloc] init];
 
 		[_settings reload];
 	} @catch (id e) {
 		[self release];
 		@throw e;
@@ -599,10 +614,11 @@
 	[_IPv6Socket cancelAsyncRequests];
 	[_IPv6Socket release];
 #endif
 	[_queries release];
 	[_TCPQueries release];
+	[_cache release];
 
 	[super dealloc];
 }
 
 - (OFDictionary *)staticHosts
@@ -802,10 +818,29 @@
 		 delegate: (id <OFDNSResolverQueryDelegate>)delegate
 {
 	void *pool = objc_autoreleasePoolPush();
 	OFNumber *ID;
 	OFDNSResolverContext *context;
+	OFPair OF_GENERIC(OFDate *, OFDNSResponse *) *cacheEntry;
+
+	if ((cacheEntry = [_cache objectForKey: query]) != nil) {
+		uint32_t age =
+		    (uint32_t)-[cacheEntry.firstObject timeIntervalSinceNow];
+		OFDNSResponse *response = cacheEntry.secondObject;
+
+		if (!containsExpiredRecord(response.answerRecords, age) &&
+		    !containsExpiredRecord(response.authorityRecords, age) &&
+		    !containsExpiredRecord(response.additionalRecords, age)) {
+			[delegate resolver: self
+			   didPerformQuery: query
+				  response: response
+				 exception: nil];
+
+			objc_autoreleasePoolPop(pool);
+			return;
+		}
+	}
 
 	/* Random, unused ID */
 	do {
 		ID = [OFNumber numberWithUnsignedShort: OFRandom16()];
 	} while ([_queries objectForKey: ID] != nil);
@@ -1038,10 +1073,17 @@
 	}
 
 	if (exception != nil)
 		response = nil;
 
+	if (response != nil)
+		[_cache setObject: [OFPair pairWithFirstObject: [OFDate date]
+						  secondObject: response]
+			   forKey: context->_query];
+	else
+		[_cache removeObjectForKey: context->_query];
+
 	[context->_delegate resolver: self
 		     didPerformQuery: context->_query
 			    response: response
 			   exception: exception];