diff --git a/configure.ac b/configure.ac
index 14eeec3..a328522 100644
--- a/configure.ac
+++ b/configure.ac
@@ -61,6 +61,12 @@ if test ! -f "$srcdir/src/glsl/glcpp/glcpp-parse.c"; then
     fi
 fi
 AC_PROG_LEX
+AC_PATH_PROG([LEX_INST], $LEX)
+if test ! -f "$srcdir/src/glsl/glcpp/glcpp-lex.c"; then
+    if test -z "$LEX_INST"; then
+        AC_MSG_ERROR([lex not found - unable to compile glcpp-lex.y])
+    fi
+fi
 
 AC_PATH_PROG([PERL], [perl])