Index: src/OFTarArchive.m
==================================================================
--- src/OFTarArchive.m
+++ src/OFTarArchive.m
@@ -294,11 +294,11 @@
 		@throw [OFNotOpenException exceptionWithObject: self];
 
 	if (_atEndOfStream)
 		return 0;
 
-	if (length > UINT64_MAX)
+	if (sizeof(length) >= sizeof(uint64_t) && length > UINT64_MAX)
 		@throw [OFOutOfRangeException exception];
 
 	if ((uint64_t)length > _toRead)
 		length = (size_t)_toRead;
 

Index: src/OFZIPArchive.m
==================================================================
--- src/OFZIPArchive.m
+++ src/OFZIPArchive.m
@@ -751,11 +751,11 @@
 		@throw [OFNotOpenException exceptionWithObject: self];
 
 	if (_atEndOfStream)
 		return 0;
 
-	if (length > UINT64_MAX)
+	if (sizeof(length) >= sizeof(uint64_t) && length > UINT64_MAX)
 		@throw [OFOutOfRangeException exception];
 
 	if ((uint64_t)length > _toRead)
 		length = (size_t)_toRead;
 
@@ -808,11 +808,12 @@
 }
 
 - (void)lowlevelWriteBuffer: (const void *)buffer
 		     length: (size_t)length
 {
-	if (length > INT64_MAX || INT64_MAX - _bytesWritten < (int64_t)length)
+	if ((sizeof(length) >= sizeof(int64_t) && length > INT64_MAX) ||
+	    INT64_MAX - _bytesWritten < (int64_t)length)
 		@throw [OFOutOfRangeException exception];
 
 	[_stream writeBuffer: buffer
 		      length: length];