diff --git a/assembler/test/rnde-intsrc.g4a b/assembler/test/rnde-intsrc.g4a
index 53bfc186..68562fa2 100644
--- a/assembler/test/rnde-intsrc.g4a
+++ b/assembler/test/rnde-intsrc.g4a
@@ -1 +1,2 @@
+/* Non-float types are not permitted in the sources of round instructions. */
 rnde (1) g0<1>UD g1<0,1,0>UD { align1 };