diff --git a/src/backend/access/brin/brin_minmax_multi.c b/src/backend/access/brin/brin_minmax_multi.c
index ac670fd02d7..be03d61c4ca 100644
--- a/src/backend/access/brin/brin_minmax_multi.c
+++ b/src/backend/access/brin/brin_minmax_multi.c
@@ -2364,14 +2364,14 @@ brin_minmax_multi_distance_inet(PG_FUNCTION_ARGS)
 		unsigned char mask;
 		int			nbits;
 
-		nbits = lena - (i * 8);
+		nbits = Max(0, lena - (i * 8));
 		if (nbits < 8)
 		{
 			mask = (0xFF << (8 - nbits));
 			addra[i] = (addra[i] & mask);
 		}
 
-		nbits = lenb - (i * 8);
+		nbits = Max(0, lenb - (i * 8));
 		if (nbits < 8)
 		{
 			mask = (0xFF << (8 - nbits));