kc3-lang/kc3

diff --git a/config.subr b/config.subr
index c5dcc3e..6134807 100644
--- a/config.subr
+++ b/config.subr
@@ -258,11 +258,11 @@ fi
 echo "GROUP = $GROUP" >> ${CONFIG_MK}
 
 if [ "x$BINDIR" = "x" ]; then
-    BINDIR=${PREFIX}/bin
+    BINDIR="${PREFIX}/bin"
 fi
 echo "BINDIR = $BINDIR" >> ${CONFIG_MK}
 
 if [ "x$LIBDIR" = "x" ]; then
-    LIBDIR=${PREFIX}/lib
+    LIBDIR="${PREFIX}/lib"
 fi
 echo "LIBDIR = $LIBDIR" >> ${CONFIG_MK}
diff --git a/configure b/configure
index c7e72f3..3e6aa6b 100755
--- a/configure
+++ b/configure
@@ -15,7 +15,7 @@ set -e
 
 export SRC_TOP="$(pwd)"
 
-PREFIX="${PREFIX:-/usr/local}"
+: ${PREFIX:=/usr/local}
 if [ "x$1" = "x--prefix" ]; then
     PREFIX="$2"
     shift 2