diff --git a/libraries/libregf/libregf.SlackBuild b/libraries/libregf/libregf.SlackBuild
index b8d64e72b2..81b1d134c9 100644
--- a/libraries/libregf/libregf.SlackBuild
+++ b/libraries/libregf/libregf.SlackBuild
@@ -72,8 +72,8 @@ find -L . \
  \( -perm 666 -o -perm 664 -o -perm 640 -o -perm 600 -o -perm 444 \
   -o -perm 440 -o -perm 400 \) -exec chmod 644 {} \;
 
-CFLAGS="$SLKCFLAGS" \
-CXXFLAGS="$SLKCFLAGS" \
+CFLAGS="$SLKCFLAGS -std=gnu89" \
+CXXFLAGS="$SLKCFLAGS -std=gnu89" \
 ./configure \
   --prefix=/usr \
   --libdir=/usr/lib${LIBDIRSUFFIX} \