diff --git a/sys/netinet6/ipcomp_core.c b/sys/netinet6/ipcomp_core.c
index bf12545ae786..62af1bc6398f 100644
--- a/sys/netinet6/ipcomp_core.c
+++ b/sys/netinet6/ipcomp_core.c
@@ -252,14 +252,17 @@ do { \
 			MOREBLOCK();
 		}
 
-		zerror = mode ? inflate(&zs, Z_FINISH)
+		zerror = mode ? inflate(&zs, Z_SYNC_FLUSH)
 			      : deflate(&zs, Z_FINISH);
 
 		if (zerror == Z_STREAM_END)
 			break;
-		else if (zerror == Z_OK)
-			; /* once more. */
-		else {
+		else if (zerror == Z_OK) {
+			if (mode && zs.avail_out != 0)
+				goto terminate;
+			else
+				; /* once more. */
+		} else {
 			if (zs.msg) {
 				ipseclog((LOG_ERR, "ipcomp_%scompress: "
 				    "%sflate(Z_FINISH): %s\n",