diff --git a/README.md b/README.md
index 3e60e633bd..600ace9f28 100644
--- a/README.md
+++ b/README.md
@@ -64,8 +64,8 @@ depending on whether you are on a 32-bit or 64-bit system, or you can
 [click here](https://github.com/rdb/panda3d-thirdparty) for instructions on
 building them from source.
 
-- https://www.panda3d.org/download/panda3d-1.10.8/panda3d-1.10.8-tools-win64.zip
-- https://www.panda3d.org/download/panda3d-1.10.8/panda3d-1.10.8-tools-win32.zip
+- https://www.panda3d.org/download/panda3d-1.10.9/panda3d-1.10.9-tools-win64.zip
+- https://www.panda3d.org/download/panda3d-1.10.9/panda3d-1.10.9-tools-win32.zip
 
 After acquiring these dependencies, you can build Panda3D from the command
 prompt using the following command.  Change the `--msvc-version` option based
diff --git a/makepanda/makepanda.py b/makepanda/makepanda.py
index bbb8e3bc7a..fe7558c049 100755
--- a/makepanda/makepanda.py
+++ b/makepanda/makepanda.py
@@ -1453,6 +1453,19 @@ def CompileFlex(wobj,wsrc,opts):
     pre = GetValueOption(opts, "BISONPREFIX_")
     dashi = opts.count("FLEXDASHI")
     flex = GetFlex()
+    want_version = GetValueOption(opts, "FLEXVERSION:")
+    if flex and want_version:
+        # Is flex at the required version for this file?
+        want_version = tuple(map(int, want_version.split('.')))
+        have_version = GetFlexVersion()
+        if want_version > have_version:
+            Warn("Skipping flex %s for file %s, need at least %s" % (
+                '.'.join(map(str, have_version)),
+                ifile,
+                '.'.join(map(str, want_version)),
+            ))
+            flex = None
+
     if flex is None:
         # We don't have flex.  See if there is a prebuilt file.
         base, ext = os.path.splitext(wsrc)
@@ -4383,7 +4396,7 @@ if GetTarget() == 'windows' and not PkgSkip("DX9"):
 #
 
 if not PkgSkip("EGG"):
-    OPTS=['DIR:panda/src/egg', 'BUILDING:PANDAEGG', 'ZLIB', 'BISONPREFIX_eggyy', 'FLEXDASHI']
+    OPTS=['DIR:panda/src/egg', 'BUILDING:PANDAEGG', 'ZLIB', 'BISONPREFIX_eggyy', 'FLEXDASHI', 'FLEXVERSION:2.5.9']
     CreateFile(GetOutputDir()+"/include/parser.h")
     TargetAdd('p3egg_parser.obj', opts=OPTS, input='parser.yxx')
     TargetAdd('parser.h', input='p3egg_parser.obj', opts=['DEPENDENCYONLY'])
diff --git a/makepanda/makepandacore.py b/makepanda/makepandacore.py
index ca801948c4..200f24dbdb 100644
--- a/makepanda/makepandacore.py
+++ b/makepanda/makepandacore.py
@@ -552,6 +552,23 @@ def GetFlex():
 
     return FLEX
 
+def GetFlexVersion():
+    flex = GetFlex()
+    if not flex:
+        return (0, 0, 0)
+
+    try:
+        handle = subprocess.Popen(["flex", "--version"], executable=flex, stdout=subprocess.PIPE)
+        words = handle.communicate()[0].strip().splitlines()[0].split(b' ')
+        if words[1] != "version":
+            version = words[1]
+        else:
+            version = words[2]
+        return tuple(map(int, version.split(b'.')))
+    except:
+        Warn("Unable to detect flex version")
+        return (0, 0, 0)
+
 ########################################################################
 ##
 ## LocateBinary
diff --git a/panda/src/egg/eggNode_ext.h b/panda/src/egg/eggNode_ext.h
index aa94aa41cd..41127667a6 100644
--- a/panda/src/egg/eggNode_ext.h
+++ b/panda/src/egg/eggNode_ext.h
@@ -19,6 +19,7 @@
 #ifdef HAVE_PYTHON
 
 #include "extension.h"
+#include "eggData.h"
 #include "eggNode.h"
 #include "py_panda.h"
 
diff --git a/panda/src/egg/lexer.cxx.prebuilt b/panda/src/egg/lexer.cxx.prebuilt
index 178bb5c152..16ca6eff9d 100644
--- a/panda/src/egg/lexer.cxx.prebuilt
+++ b/panda/src/egg/lexer.cxx.prebuilt
@@ -1195,12 +1195,12 @@ scan_quoted_string() {
 
   int c;
   c = read_char(line, col);
-  while (c != '"' && c != EOF) {
+  while (c != '"' && c != 0 && c != EOF) {
     result += c;
     c = read_char(line, col);
   }
 
-  if (c == EOF) {
+  if (c == 0 || c == EOF) {
     eggyyerror("This quotation mark is unterminated.");
   }
 
@@ -1224,7 +1224,7 @@ eat_c_comment() {
   
   last_c = '\0';
   c = read_char(line, col);
-  while (c != EOF && !(last_c == '*' && c == '/')) {
+  while (c != 0 && c != EOF && !(last_c == '*' && c == '/')) {
     if (last_c == '/' && c == '*') {
       std::ostringstream errmsg;
       errmsg << "This comment contains a nested /* symbol at line "
@@ -1236,7 +1236,7 @@ eat_c_comment() {
     c = read_char(line, col);
   }
 
-  if (c == EOF) {
+  if (c == 0 || c == EOF) {
     eggyyerror("This comment marker is unclosed.");
   }
 
diff --git a/panda/src/egg/lexer.lxx b/panda/src/egg/lexer.lxx
index 88aed62e46..c4b6f88028 100644
--- a/panda/src/egg/lexer.lxx
+++ b/panda/src/egg/lexer.lxx
@@ -250,12 +250,12 @@ scan_quoted_string() {
 
   int c;
   c = read_char(line, col);
-  while (c != '"' && c != EOF) {
+  while (c != '"' && c != 0 && c != EOF) {
     result += c;
     c = read_char(line, col);
   }
 
-  if (c == EOF) {
+  if (c == 0 || c == EOF) {
     eggyyerror("This quotation mark is unterminated.");
   }
 
@@ -279,7 +279,7 @@ eat_c_comment() {
 
   last_c = '\0';
   c = read_char(line, col);
-  while (c != EOF && !(last_c == '*' && c == '/')) {
+  while (c != 0 && c != EOF && !(last_c == '*' && c == '/')) {
     if (last_c == '/' && c == '*') {
       std::ostringstream errmsg;
       errmsg << "This comment contains a nested /* symbol at line "
@@ -291,7 +291,7 @@ eat_c_comment() {
     c = read_char(line, col);
   }
 
-  if (c == EOF) {
+  if (c == 0 || c == EOF) {
     eggyyerror("This comment marker is unclosed.");
   }