diff --git a/make-includes/standard_suffixes.make b/make-includes/standard_suffixes.make
index 12df4b5..fc9f1fc 100644
--- a/make-includes/standard_suffixes.make
+++ b/make-includes/standard_suffixes.make
@@ -9,4 +9,4 @@
 #
 # Add standard file suffixes.
 #
-.SUFFIXES: .svg .pdf .tex .dvi .png .tif .plo .jpg .pict .eps .ps .R .xml
+.SUFFIXES: .svg .pdf .tex .dvi .png .tif .plo .jpg .pict .eps .ps .R .xml .pu .ipu