diff --git a/dev-libs/libksba/libksba-1.3.5-r2.ebuild b/dev-libs/libksba/libksba-1.3.5-r2.ebuild
index b8c1d0eee738c..ef29c486e9a71 100644
--- a/dev-libs/libksba/libksba-1.3.5-r2.ebuild
+++ b/dev-libs/libksba/libksba-1.3.5-r2.ebuild
@@ -17,7 +17,8 @@ DEPEND="${RDEPEND}"
 
 src_configure() {
 	econf \
-		$(use_enable static-libs static)
+		$(use_enable static-libs static) \
+		$(./configure --help | grep -- --with-.*-prefix | sed -e 's/prefix.*/prefix/' -e "s#\$#=${EROOT}/usr#")
 }
 
 src_install() {