diff --git a/Dockerfile b/Dockerfile
index 3eda9a4..ebd915c 100644
--- a/Dockerfile
+++ b/Dockerfile
@@ -49,6 +49,14 @@ RUN sed -i 's/-zx/-ozx/g' \
   /usr/class/assignments/PA4J/grade.pl /usr/class/assignments/PA4/grade.pl \
   /usr/class/assignments/PA5J/grade.pl /usr/class/assignments/PA5/grade.pl
 
+# Patch cool.flex in submission folder
+# This is a hack to
+#   a) satisfy the cool compiler which expects yylex to be named cool_yylex
+#   b) satisfy libfl > 2.5.39 which expects a yylex symbol
+#   c) fix mangling errors of yylex when compiled with a c++ compiler
+#   d) be as non-invasive as possible to the existing assignment code
+RUN patch -u /usr/class/assignments/PA2/cool.flex -i cool.flex.patch
+
 # Setup working directory
 RUN mkdir -p /class
 WORKDIR /class
diff --git a/cool.flex.patch b/cool.flex.patch
new file mode 100644
index 0000000..a9d5f6a
--- /dev/null
+++ b/cool.flex.patch
@@ -0,0 +1,20 @@
+--- cool.flex	2011-06-18 03:22:02.000000000 +0000
++++ cool.flex.work	2020-12-19 22:43:35.902153646 +0000
+@@ -12,6 +12,17 @@
+ #include <stringtab.h>
+ #include <utilities.h>
+ 
++/* This is a hack to
++ * a) satisfy the cool compiler which expects yylex to be named cool_yylex (see below)
++ * b) satisfy libfl > 2.5.39 which expects a yylex symbol
++ * c) fix mangling errors of yylex when compiled with a c++ compiler
++ * d) be as non-invasive as possible to the existing assignment code
++ */
++extern int cool_yylex();
++extern "C" {
++  int (&yylex) (void) = cool_yylex;
++}
++
+ /* The compiler assumes these identifiers. */
+ #define yylval cool_yylval
+ #define yylex  cool_yylex