diff --git a/revision.c b/revision.c
index 33d092c..6584713 100644
--- a/revision.c
+++ b/revision.c
@@ -1209,8 +1209,6 @@
 
 			opts = diff_opt_parse(&revs->diffopt, argv+i, argc-i);
 			if (opts > 0) {
-				if (strcmp(argv[i], "-z"))
-					revs->diff = 1;
 				i += opts - 1;
 				continue;
 			}
@@ -1254,6 +1252,14 @@
 		add_pending_object_with_mode(revs, object, def, mode);
 	}
 
+	/* Did the user ask for any diff output? Run the diff! */
+	if (revs->diffopt.output_format & ~DIFF_FORMAT_NO_OUTPUT)
+		revs->diff = 1;
+
+	/* Pickaxe needs diffs */
+	if (revs->diffopt.pickaxe)
+		revs->diff = 1;
+
 	if (revs->topo_order)
 		revs->limited = 1;