diff --git a/compr_rtime.c b/compr_rtime.c
index 131536c..7353024 100644
--- a/compr_rtime.c
+++ b/compr_rtime.c
@@ -32,7 +32,7 @@ static int jffs2_rtime_compress(unsigned char *data_in, unsigned char *cpage_out
 
 	memset(positions,0,sizeof(positions));
 
-	while (pos < (*sourcelen) && outpos <= (*dstlen)-2) {
+	while (pos < (*sourcelen) && outpos+2 <= *dstlen) {
 		int backpos, runlen=0;
 		unsigned char value;
 
diff --git a/compr_zlib.c b/compr_zlib.c
index 400b18a..eb415b9 100644
--- a/compr_zlib.c
+++ b/compr_zlib.c
@@ -71,7 +71,7 @@ int jffs2_zlib_compress(unsigned char *data_in, unsigned char *cpage_out,
 	strm.next_out = cpage_out;
 	strm.total_out = 0;
 
-	while (strm.total_out < *dstlen - STREAM_END_SPACE && strm.total_in < *sourcelen) {
+	while (strm.total_out + STREAM_END_SPACE < *dstlen && strm.total_in < *sourcelen) {
 		strm.avail_out = *dstlen - (strm.total_out + STREAM_END_SPACE);
 		strm.avail_in = min((unsigned)(*sourcelen-strm.total_in), strm.avail_out);
 		ret = deflate(&strm, Z_PARTIAL_FLUSH);