diff --git a/builtin/log.c b/builtin/log.c
index 63875c3aee..c3caf0955b 100644
--- a/builtin/log.c
+++ b/builtin/log.c
@@ -723,10 +723,6 @@ static void log_setup_revisions_tweak(struct rev_info *rev,
 	    rev->prune_data.nr == 1)
 		rev->diffopt.flags.follow_renames = 1;
 
-	/* Turn --cc/-c into -p --cc/-c when -p was not given */
-	if (!rev->diffopt.output_format && rev->combine_merges)
-		rev->diffopt.output_format = DIFF_FORMAT_PATCH;
-
 	if (rev->first_parent_only)
 		diff_merges_default_to_first_parent(rev);
 }
diff --git a/diff-merges.c b/diff-merges.c
index fb591a9339..c48a65f8de 100644
--- a/diff-merges.c
+++ b/diff-merges.c
@@ -102,4 +102,9 @@ void diff_merges_setup_revs(struct rev_info *revs)
 		revs->ignore_merges = 1;
 	if (revs->combined_all_paths && !revs->combine_merges)
 		die("--combined-all-paths makes no sense without -c or --cc");
+	if (revs->combine_merges) {
+		/* Turn --cc/-c into -p --cc/-c when -p was not given */
+		if (!revs->diffopt.output_format)
+			revs->diffopt.output_format = DIFF_FORMAT_PATCH;
+	}
 }