diff --git a/read-cache.c b/read-cache.c
index 52ffa8a313..a50f1047d3 100644
--- a/read-cache.c
+++ b/read-cache.c
@@ -1276,7 +1276,7 @@ static int add_index_entry_with_check(struct index_state *istate, struct cache_e
 	 */
 	if (istate->cache_nr > 0 &&
 		strcmp(ce->name, istate->cache[istate->cache_nr - 1]->name) > 0)
-		pos = -istate->cache_nr - 1;
+		pos = -1 - istate->cache_nr;
 	else
 		pos = index_name_stage_pos(istate, ce->name, ce_namelen(ce), ce_stage(ce));
 
@@ -1894,7 +1894,7 @@ static size_t estimate_cache_size(size_t ondisk_size, unsigned int entries)
 	/*
 	 * Account for potential alignment differences.
 	 */
-	per_entry += align_padding_size(sizeof(struct cache_entry), -sizeof(struct ondisk_cache_entry));
+	per_entry += align_padding_size(per_entry, 0);
 	return ondisk_size + entries * per_entry;
 }
 
diff --git a/sha1-lookup.c b/sha1-lookup.c
index 796ab68da8..c819687730 100644
--- a/sha1-lookup.c
+++ b/sha1-lookup.c
@@ -97,7 +97,7 @@ int sha1_pos(const unsigned char *sha1, void *table, size_t nr,
 			lo = mi + 1;
 		mi = lo + (hi - lo) / 2;
 	} while (lo < hi);
-	return -lo-1;
+	return -1 - lo;
 }
 
 int bsearch_hash(const unsigned char *sha1, const uint32_t *fanout_nbo,