Index: head/Mk/Scripts/check-stagedir.sh
===================================================================
--- head/Mk/Scripts/check-stagedir.sh
+++ head/Mk/Scripts/check-stagedir.sh
@@ -224,20 +224,8 @@
 esac
 
 # validate environment
-envfault=
-for i in STAGEDIR PREFIX LOCALBASE WRKDIR WRKSRC MTREE_FILE \
-    TMPPLIST PLIST_SUB_SED SCRIPTSDIR \
-    PORT_OPTIONS NO_PREFIX_RMDIR
-do
-    if ! ( eval ": \${${i}?}" ) 2>/dev/null ; then
-		envfault="${envfault}${envfault:+" "}${i}"
-    fi
-done
-if [ -n "$envfault" ] ; then
-	echo "Environment variables $envfault undefined. Aborting." \
-	| fmt >&2
-	exit 1
-fi
+validate_env STAGEDIR PREFIX LOCALBASE WRKDIR WRKSRC MTREE_FILE \
+    TMPPLIST PLIST_SUB_SED SCRIPTSDIR PORT_OPTIONS NO_PREFIX_RMDIR
 
 set -u
 
Index: head/Mk/Scripts/do-depends.sh
===================================================================
--- head/Mk/Scripts/do-depends.sh
+++ head/Mk/Scripts/do-depends.sh
@@ -7,22 +7,11 @@
 
 . ${dp_SCRIPTSDIR}/functions.sh
 
-envfault=
-for i in dp_RAWDEPENDS dp_DEPTYPE dp_DEPENDS_TARGET dp_DEPENDS_PRECLEAN \
+validate_env dp_RAWDEPENDS dp_DEPTYPE dp_DEPENDS_TARGET dp_DEPENDS_PRECLEAN \
 	dp_DEPENDS_CLEAN dp_DEPENDS_ARGS dp_USE_PACKAGE_DEPENDS \
 	dp_USE_PACKAGE_DEPENDS_ONLY dp_PKG_ADD dp_PKG_INFO dp_WRKDIR \
 	dp_PKGNAME dp_STRICT_DEPENDS dp_LOCALBASE dp_LIB_DIRS dp_SH \
 	dp_SCRIPTSDIR dp_PORTSDIR dp_MAKE
-do
-	if ! (eval ": \${${i}?}" ) >/dev/null; then
-		envfault="${envfault}${envfault:+" "}${i}"
-	fi
-done
-if [ -n "${envfault}" ]; then
-	echo "Environment variable ${envfault} undefined. Aborting." \
-		| fmt >&2
-	exit 1
-fi
 
 set -u
 
Index: head/Mk/Scripts/functions.sh
===================================================================
--- head/Mk/Scripts/functions.sh
+++ head/Mk/Scripts/functions.sh
@@ -139,3 +139,17 @@
 		esac
 	done
 }
+
+validate_env() {
+	local envfault
+	for i ; do
+		if ! (eval ": \${${i}?}" ) >/dev/null; then
+			envfault="${envfault}${envfault:+" "}${i}"
+		fi
+	done
+	if [ -n "${envfault}" ]; then
+		echo "Environment variable ${envfault} undefined. Aborting." \
+		| fmt >&2
+		exit 1
+	fi
+}