diff --git a/revision.c b/revision.c
index 064e351084..eb0be4206d 100644
--- a/revision.c
+++ b/revision.c
@@ -416,7 +416,7 @@ static int rev_same_tree_as_empty(struct rev_info *revs, struct commit *commit)
 static void try_to_simplify_commit(struct rev_info *revs, struct commit *commit)
 {
 	struct commit_list **pp, *parent;
-	int tree_changed = 0, tree_same = 0;
+	int tree_changed = 0, tree_same = 0, nth_parent = 0;
 
 	/*
 	 * If we don't do pruning, everything is interesting
@@ -444,6 +444,14 @@ static void try_to_simplify_commit(struct rev_info *revs, struct commit *commit)
 	while ((parent = *pp) != NULL) {
 		struct commit *p = parent->item;
 
+		/*
+		 * Do not compare with later parents when we care only about
+		 * the first parent chain, in order to avoid derailing the
+		 * traversal to follow a side branch that brought everything
+		 * in the path we are limited to by the pathspec.
+		 */
+		if (revs->first_parent_only && nth_parent++)
+			break;
 		if (parse_commit(p) < 0)
 			die("cannot simplify commit %s (because of %s)",
 			    sha1_to_hex(commit->object.sha1),
diff --git a/t/t6012-rev-list-simplify.sh b/t/t6012-rev-list-simplify.sh
index af34a1e817..839ad97b79 100755
--- a/t/t6012-rev-list-simplify.sh
+++ b/t/t6012-rev-list-simplify.sh
@@ -86,5 +86,6 @@ check_result 'I H E C B A' --full-history --date-order -- file
 check_result 'I E C B A' --simplify-merges -- file
 check_result 'I B A' -- file
 check_result 'I B A' --topo-order -- file
+check_result 'H' --first-parent -- another-file
 
 test_done