diff --git a/configure.ac b/configure.ac
index 8823288..78d0af9 100644
--- a/configure.ac
+++ b/configure.ac
@@ -93,6 +93,7 @@
 if test x"$werror" = x"yes"
 then
 	WERROR_FLAGS="-Werror"
+	WERROR_FLAGS+=" -Werror=implicit-int -Werror=int-conversion -Werror=old-style-definition"
 	WERROR_FLAGS+=" -Wno-error=deprecated -Wno-error=deprecated-declarations"
 	WERROR_FLAGS+=" -Wno-error=cpp" # "#warning"
 	CFLAGS="$CFLAGS $WERROR_FLAGS"