Index: src/OFString+URLEncoding.m
==================================================================
--- src/OFString+URLEncoding.m
+++ src/OFString+URLEncoding.m
@@ -21,10 +21,11 @@
 
 #import "OFString+URLEncoding.h"
 #import "OFCharacterSet.h"
 
 #import "OFInvalidFormatException.h"
+#import "OFInvalidEncodingException.h"
 #import "OFOutOfMemoryException.h"
 
 /* Reference for static linking */
 int _OFString_URLEncoding_reference;
 
@@ -46,20 +47,31 @@
 		if (characterIsMember(allowedCharacters,
 		    @selector(characterIsMember:), c))
 			[ret appendCharacters: &c
 				       length: 1];
 		else {
-			unsigned char high = c >> 4;
-			unsigned char low = c & 0x0F;
-			of_unichar_t escaped[3];
-
-			escaped[0] = '%';
-			escaped[1] = (high > 9 ? high - 10 + 'A' : high + '0');
-			escaped[2] = (low  > 9 ? low  - 10 + 'A' : low  + '0');
-
-			[ret appendCharacters: escaped
-				       length: 3];
+			char buffer[4];
+			size_t bufferLen;
+
+			if ((bufferLen = of_string_utf8_encode(c, buffer)) == 0)
+				@throw [OFInvalidEncodingException exception];
+
+			for (size_t j = 0; j < bufferLen; j++) {
+				unsigned char byte = buffer[j];
+				unsigned char high = byte >> 4;
+				unsigned char low = byte & 0x0F;
+				char escaped[3];
+
+				escaped[0] = '%';
+				escaped[1] =
+				    (high > 9 ? high - 10 + 'A' : high + '0');
+				escaped[2] =
+				    (low  > 9 ? low  - 10 + 'A' : low  + '0');
+
+				[ret appendUTF8String: escaped
+					       length: 3];
+			}
 		}
 	}
 
 	objc_autoreleasePoolPop(pool);
 

Index: tests/OFStringTests.m
==================================================================
--- tests/OFStringTests.m
+++ tests/OFStringTests.m
@@ -781,18 +781,19 @@
 
 	TEST(@"-[SHA512Hash]", [[C(@"asdfoobar") SHA512Hash] isEqual:
 	    @"0464c427da158b02161bb44a3090bbfc594611ef6a53603640454b56412a9247c"
 	    @"3579a329e53a5dc74676b106755e3394f9454a2d42273242615d32f80437d61"])
 
+	OFCharacterSet *cs = [OFCharacterSet
+	    characterSetWithCharactersInString: @"abfo'_~$🍏"];
 	TEST(@"-[stringByURLEncodingWithAllowedCharacters:]",
-	    [[C(@"foo\"ba'_~$]") stringByURLEncodingWithAllowedCharacters:
-	    [OFCharacterSet URLPathAllowedCharacterSet]]
-	    isEqual: @"foo%22ba'_~$%5D"])
+	    [[C(@"foo\"ba'_~$]🍏🍌") stringByURLEncodingWithAllowedCharacters:
+	    cs] isEqual: @"foo%22ba'_~$%5D🍏%F0%9F%8D%8C"])
 
 	TEST(@"-[stringByURLDecoding]",
-	    [[C(@"foo%20bar%22+%24") stringByURLDecoding]
-	    isEqual: @"foo bar\"+$"])
+	    [[C(@"foo%20bar%22+%24%F0%9F%8D%8C") stringByURLDecoding]
+	    isEqual: @"foo bar\"+$🍌"])
 
 	TEST(@"-[insertString:atIndex:]",
 	    (s[0] = [mutableStringClass stringWithString: @"𝄞öööbä€"]) &&
 	    R([s[0] insertString: @"äöü"
 			 atIndex: 3]) &&