diff --git a/extensions/unratified/rv64_zish4add b/extensions/unratified/rv64_zish4add
new file mode 100644
index 00000000..23f91551
--- /dev/null
+++ b/extensions/unratified/rv64_zish4add
@@ -0,0 +1,5 @@
+#adjacent to sh[123]add
+sh4add     rd rs1 rs2 31..25=16 14..12=7 6..2=0x0C 1..0=3
+
+#adjacent to sh[123]add.uw
+sh4add.uw  rd rs1 rs2 31..25=16 14..12=7 6..2=0x0E 1..0=3