diff --git a/lib/mpi/mpih-div.c b/lib/mpi/mpih-div.c
index 87ede162..cde1aae 100644
--- a/lib/mpi/mpih-div.c
+++ b/lib/mpi/mpih-div.c
@@ -217,6 +217,10 @@
 	case 0:
 		/* We are asked to divide by zero, so go ahead and do it!  (To make
 		   the compiler not remove this statement, return the value.)  */
+		/*
+		 * existing clients of this function have been modified
+		 * not to call it with dsize == 0, so this should not happen
+		 */
 		return 1 / dsize;
 
 	case 1: