diff --git a/make-includes/build_lecture_rules.make b/make-includes/build_lecture_rules.make
index 5d3703e..8908ed6 100644
--- a/make-includes/build_lecture_rules.make
+++ b/make-includes/build_lecture_rules.make
@@ -45,6 +45,12 @@
 #
 # Various environment variables.
 #
+# Important: default font size for Beamer is 11pt. We need to define this before
+# loading the standard environment. However, allow the user to override it!
+ifndef FONT_SIZE
+FONT_SIZE=11pt
+endif
+
 include $(GLOBAL_HANDBOOK_INCLUDE)/standard_environment.make
 #
 # Base file names for the various documents.
@@ -84,7 +90,7 @@
 
 ################################################################################
 #
-# Alternate LaTeXs for Unicode vs. non-Unicode provessing.
+# Alternate LaTeXs for Unicode vs. non-Unicode processing.
 #
 ifdef UNICODE
 LATEXCMD:=$(XELATEX)