Index: src/OFMutableString_UTF8.m
==================================================================
--- src/OFMutableString_UTF8.m
+++ src/OFMutableString_UTF8.m
@@ -393,40 +393,20 @@
 	@try {
 		size_t i, j = 0;
 		bool isUTF8 = false;
 
 		for (i = 0; i < length; i++) {
-			char buffer[4];
-
-			switch (of_string_utf8_encode(characters[i], buffer)) {
-			case 1:
-				tmp[j++] = buffer[0];
-				break;
-			case 2:
-				isUTF8 = true;
-
-				memcpy(tmp + j, buffer, 2);
-				j += 2;
-
-				break;
-			case 3:
-				isUTF8 = true;
-
-				memcpy(tmp + j, buffer, 3);
-				j += 3;
-
-				break;
-			case 4:
-				isUTF8 = true;
-
-				memcpy(tmp + j, buffer, 4);
-				j += 4;
-
-				break;
-			default:
-				@throw [OFInvalidEncodingException exception];
-			}
+			size_t len = of_string_utf8_encode(characters[i],
+			    tmp + j);
+
+			if (len == 0)
+				@throw [OFInvalidEncodingException exception];
+
+			if (len > 1)
+				isUTF8 = true;
+
+			j += len;
 		}
 
 		tmp[j] = '\0';
 
 		_s->hashed = false;

Index: src/OFString_UTF8.m
==================================================================
--- src/OFString_UTF8.m
+++ src/OFString_UTF8.m
@@ -414,30 +414,20 @@
 
 		_s->cString = [self allocMemoryWithSize: (length * 4) + 1];
 		_s->length = length;
 
 		for (i = 0; i < length; i++) {
-			char buffer[4];
 			size_t len = of_string_utf8_encode(characters[i],
-			    buffer);
-
-			switch (len) {
-			case 1:
-				_s->cString[j++] = buffer[0];
-				break;
-			case 2:
-			case 3:
-			case 4:
+			    _s->cString + j);
+
+			if (len == 0)
+				@throw [OFInvalidEncodingException exception];
+
+			if (len > 1)
 				_s->isUTF8 = true;
 
-				memcpy(_s->cString + j, buffer, len);
-				j += len;
-
-				break;
-			default:
-				@throw [OFInvalidEncodingException exception];
-			}
+			j += len;
 		}
 
 		_s->cString[j] = '\0';
 		_s->cStringLength = j;
 
@@ -479,11 +469,10 @@
 
 		_s->cString = [self allocMemoryWithSize: (length * 4) + 1];
 		_s->length = length;
 
 		for (i = 0; i < length; i++) {
-			char buffer[4];
 			of_unichar_t character =
 			    (swap ? OF_BSWAP16(string[i]) : string[i]);
 			size_t len;
 
 			/* Missing high surrogate */
@@ -510,28 +499,19 @@
 
 				i++;
 				_s->length--;
 			}
 
-			len = of_string_utf8_encode(character, buffer);
-
-			switch (len) {
-			case 1:
-				_s->cString[j++] = buffer[0];
-				break;
-			case 2:
-			case 3:
-			case 4:
+			len = of_string_utf8_encode(character, _s->cString + j);
+
+			if (len == 0)
+				@throw [OFInvalidEncodingException exception];
+
+			if (len > 1)
 				_s->isUTF8 = true;
 
-				memcpy(_s->cString + j, buffer, len);
-				j += len;
-
-				break;
-			default:
-				@throw [OFInvalidEncodingException exception];
-			}
+			j += len;
 		}
 
 		_s->cString[j] = '\0';
 		_s->cStringLength = j;