diff --git a/sch2fig/misc.c b/sch2fig/misc.c
index a946edc..820464a 100644
--- a/sch2fig/misc.c
+++ b/sch2fig/misc.c
@@ -37,6 +37,10 @@ unsigned matrix_to_angle(int m[6])
 		return 270;
 	if (eq(m, -1, 0, 0, -1))
 		return 0;
+	if (eq(m, 1, 0, 0, 1))	/* x-flipped */
+		return 180;
+	if (eq(m, 0, 1, -1, 0))	/* x-flipped, 90 deg */
+		return 90;
 	fprintf(stderr, "unrecognized matrix %d %d %d %d\n",
 	    m[1], m[2], m[4], m[5]);
 	exit(1);
@@ -56,6 +60,10 @@ bool matrix_is_mirrored(int m[6])
 
 	if (eq(m, -1, 0, 0, -1))
 		return 1;
+	if (eq(m, 1, 0, 0, 1))
+		return 1;
+	if (eq(m, 0, 1, -1, 0))
+		return 1;
 	assert(0);
 }