Index: src/OFUTF8String.m
==================================================================
--- src/OFUTF8String.m
+++ src/OFUTF8String.m
@@ -370,23 +370,26 @@
 			unsigned char character = (unsigned char)cString[i];
 			OFUnichar unichar;
 			char buffer[4];
 			size_t byteLength;
 
-			if (character < tableOffset) {
-				_s->cString[j++] = cString[i];
-				continue;
-			}
-
-			unichar = table[character - tableOffset];
+			if (character >= tableOffset)
+				unichar = table[character - tableOffset];
+			else
+				unichar = character;
 
 			if (unichar == 0xFFFF)
 				@throw [OFInvalidEncodingException exception];
+
+			if (unichar < 0x7F) {
+				_s->cString[j++] = (char)unichar;
+				continue;
+			}
 
 			_s->isUTF8 = true;
+
 			byteLength = _OFUTF8StringEncode(unichar, buffer);
-
 			if (byteLength == 0)
 				@throw [OFInvalidEncodingException exception];
 
 			_s->cStringLength += byteLength - 1;
 			_s->cString = OFResizeMemory(_s->cString,

Index: tests/OFStringTests.m
==================================================================
--- tests/OFStringTests.m
+++ tests/OFStringTests.m
@@ -263,12 +263,13 @@
 
 #ifdef HAVE_ISO_8859_15
 - (void)testStringWithCStringEncodingISO8859_15
 {
 	OTAssertEqualObjects([self.stringClass
-	    stringWithCString: "\xA4\xA6\xA8\xB4\xB8\xBC\xBD\xBE"
-		     encoding: OFStringEncodingISO8859_15], @"€ŠšŽžŒœŸ");
+	    stringWithCString: "a\x80\xA4\xA6\xA8\xB4\xB8\xBC\xBD\xBE"
+		     encoding: OFStringEncodingISO8859_15],
+	    @"a\xC2\x80€ŠšŽžŒœŸ");
 }
 #endif
 
 #ifdef HAVE_WINDOWS_1250
 - (void)testStringWithCStringEncodingWindows1250