diff --git a/src/asahi/compiler/agx_opcodes.py b/src/asahi/compiler/agx_opcodes.py
index da4b48b6f5e..cb98bf6fc18 100644
--- a/src/asahi/compiler/agx_opcodes.py
+++ b/src/asahi/compiler/agx_opcodes.py
@@ -255,3 +255,7 @@ op("or", _, srcs = 2)
 op("p_combine", _, srcs = 4)
 op("p_split", _, srcs = 1, dests = 4)
 op("p_extract", _, srcs = 1, imms = [COMPONENT])
+
+# Phis are special-cased in the IR as they (uniquely) can take an unbounded
+# number of source.
+op("phi", _, srcs = 0)