diff --git a/make-includes/build_lecture_rules.make b/make-includes/build_lecture_rules.make
index 5c1b0bb..5d1243e 100755
--- a/make-includes/build_lecture_rules.make
+++ b/make-includes/build_lecture_rules.make
@@ -347,9 +347,15 @@
 # PDF from SVG (via Inkscape)
 # We remove the intermediate file manually rather than through the tidy/clean
 # mechanism, because we might have EPS files that aren't generated by 
-# something else.
+# something else. See build_content_rules.make for explanation of ps2eps 
+# options.
+#
+# BIZARRENESS: While Inkscape produces correctly cropped EPSs in the first
+# place, if we don't run them through ps2eps first, ps2pdf has a tendency to
+# rotate the PDFs 90 degrees clockwise for no obvious reason and without any
+# apparent pattern.
 #
 %.pdf: %.svg
 	inkscape --file=$< --export-text-to-path --without-gui --export-eps=$(IMGDIR)/$*.eps
-	ps2eps --ignoreBB --nohires --loose < $(IMGDIR)/$*.eps | ps2pdf -dEPSCrop - $(IMGDIR)/$@
+	ps2eps --ignoreBB --nohires --loose --gsbbox < $(IMGDIR)/$*.eps | ps2pdf -dEPSCrop - $(IMGDIR)/$@
 	rm -f $(IMGDIR)/$*.eps