diff --git a/README.md b/README.md
index 2cbd66321..b69b8dbee 100644
--- a/README.md
+++ b/README.md
@@ -21,7 +21,7 @@ fish depends on a curses implementation, such as ncurses. The headers and librar
 
 fish requires gettext for translation support.
 
-Building the documentation requires Doxygen 1.8 or newer.
+Building the documentation requires Doxygen 1.5 or newer.
 
 ### Autotools Build
 
diff --git a/build_tools/build_documentation.sh b/build_tools/build_documentation.sh
index 77eaad687..2705898e9 100755
--- a/build_tools/build_documentation.sh
+++ b/build_tools/build_documentation.sh
@@ -68,12 +68,6 @@ if test -z "$DOXYGENPATH"; then
     exit 0
 fi
 
-# Check we have the lexicon filter
-if test -z "$INPUT_FILTER"; then
-    echo >&2 "Lexicon filter is not available. Continuing without."
-    INPUTFILTER=''
-fi
-
 # Determine where our output should go
 if ! mkdir -p "${OUTPUTDIR}" ; then
     echo "Could not create output directory '${OUTPUTDIR}'"
diff --git a/configure.ac b/configure.ac
index f36e26025..037ee8fad 100644
--- a/configure.ac
+++ b/configure.ac
@@ -146,7 +146,7 @@ AS_IF([test x$local_gettext != xno],
 # Build/clean the documentation only if Doxygen is available
 #
 
-doxygen_minimum=1.8
+doxygen_minimum=1.5
 
 AC_ARG_WITH(
   doxygen,