diff --git a/make-includes/build_lecture_rules.make b/make-includes/build_lecture_rules.make
index 728581a..4dc38a6 100644
--- a/make-includes/build_lecture_rules.make
+++ b/make-includes/build_lecture_rules.make
@@ -148,9 +148,22 @@
 ifneq ($(strip $(NOTES)),)
 
 #
+# Set the prerequisites for the "slides-notes" build target, depending on
+# whether the figures document exists. If $(FIGURES) is non-empty, we need
+# to include the figures .aux file for inter-document cross-references.
+#
+ifeq ($(strip $(FIGURES)),)
+NOTES_PREREQS:=$(NOTES).pdf
+SLIDES_NOTES_PREREQS:=slides-notes.pdf
+else
+NOTES_PREREQS:=figures $(NOTES).pdf
+SLIDES_NOTES_PREREQS:=figures slides-notes.pdf
+endif
+
+#
 # Build the slides with notes.
 #
-slides-notes: slides-notes.pdf
+slides-notes: $(SLIDES_NOTES_PREREQS)
 
 slides-notes.pdf: $(SLIDES).tex $(SLIDE_IMAGES) $(SLIDE_BACKGROUNDS) $(SLIDE_FILES)
 	$(LATEXCMD) --jobname=slides-notes '\documentclass[$(LATEX_OPTS),notes=onlyslideswithnotes]{lectureslides}\input{$(SLIDES)}'
@@ -159,7 +172,7 @@
 #
 # Build the slides with notes, 6-up.
 #
-notes: $(NOTES).pdf
+notes: $(NOTES_PREREQS)
 
 $(NOTES).pdf: $(NOTES).tex slides-notes.pdf
 	$(LATEXCMD) $<
@@ -313,10 +326,12 @@
 	@$(ECHO) "DRAFT = [$(DRAFT)]"
 	@$(ECHO) "LATEX_OPTS = [$(LATEX_OPTS)]"
 	@$(ECHO) "SLIDES = [$(SLIDES)]"
+	@$(ECHO) "SLIDES_PREREQS = [$(SLIDES_PREREQS)]"
+	@$(ECHO) "SLIDES_NOTES_PREREQS = [$(NOTES_PREREQS)]"
 	@$(ECHO) "FIGURES = [$(FIGURES)]"
 	@$(ECHO) "COMBINED = [$(COMBINED)]"
 	@$(ECHO) "NOTES = [$(NOTES)]"
-	@$(ECHO) "SLIDES_PREREQS = [$(SLIDES_PREREQS)]"
+	@$(ECHO) "NOTES_PREREQS = [$(NOTES_PREREQS)]"
 	@$(ECHO) "COMBINED_PREREQS = [$(COMBINED_PREREQS)]"
 	@$(ECHO) "TARGETS = [$(TARGETS)]"