diff --git a/docs/gudev/Makefile.am b/docs/gudev/Makefile.am
index 152cd3c018..55172f2c33 100644
--- a/docs/gudev/Makefile.am
+++ b/docs/gudev/Makefile.am
@@ -77,8 +77,8 @@ expand_content_files=
 # be listed only once.
 # Kill CFLAGS here because gtk-doc thinks adding CFLAGS to CC _and_ also
 # adding CFLAGS itself again would work.
-CFLAGS=
-LDFLAGS=
+override CFLAGS=
+override LDFLAGS=
 
 # CFLAGS and LDFLAGS for compiling gtkdoc-scangobj with your library.
 # Only needed if you are using gtkdoc-scangobj to dynamically query widget
diff --git a/docs/libudev/Makefile.am b/docs/libudev/Makefile.am
index f9365b3fd0..13e448ace0 100644
--- a/docs/libudev/Makefile.am
+++ b/docs/libudev/Makefile.am
@@ -72,6 +72,14 @@ content_files = version.xml
 # e.g. expand_content_files=running.sgml
 expand_content_files=
 
+# Hack, hack. You silly gtk-doc, you must not add  CFLAGS multiple
+# times when calling gcc; it surely can not work with options that must
+# be listed only once.
+# Kill CFLAGS here because gtk-doc thinks adding CFLAGS to CC _and_ also
+# adding CFLAGS itself again would work.
+override CFLAGS=
+override LDFLAGS=
+
 # CFLAGS and LDFLAGS for compiling gtkdoc-scangobj with your library.
 # Only needed if you are using gtkdoc-scangobj to dynamically query widget
 # signals and properties.