diff --git a/packaging/win32/functions.sh b/packaging/win32/functions.sh
index 42f79c57961..29c984734af 100644
--- a/packaging/win32/functions.sh
+++ b/packaging/win32/functions.sh
@@ -122,6 +122,7 @@ function add_to_env() {
 }
 
 # usage: set_env_or_die VALUE NAME
+# like add_to_env, but die if $NAME has been set to a different value
 function set_env_or_die() {
     _OLDADDS=`eval echo '"$'"$2_ADDS"'"'`
     add_to_env "$1" "$2"
@@ -137,6 +138,14 @@ function set_env_or_die() {
     fi
 }
 
+# usage set_env VALUE NAME
+# like $NAME=$VALUE, but also reset env tracking variables
+function set_env() {
+    eval "$2=$1"
+    eval "$2_BASE="
+    eval "$2_ADDS=$1"
+}
+
 function assert_one_dir() {
     quiet [ -d "$@" ] || die "Detected multiple directories where only one was expected; please delete all but the latest one: $@"
 }
diff --git a/packaging/win32/install.sh b/packaging/win32/install.sh
index 45a2e60aec5..ad6cfb33e76 100755
--- a/packaging/win32/install.sh
+++ b/packaging/win32/install.sh
@@ -72,10 +72,10 @@ function prepare() {
         export CFLAGS="$CFLAGS -g -O0"
     fi
 
-    if [ "$CROSS_COMPILE" ]; then
+    if [ "$CROSS_COMPILE" = "yes" ]; then
         # to avoid using the build machine's installed packages
-        export PKG_CONFIG_PATH=""
-        export PKG_CONFIG_LIBDIR=""
+        set_env "" PKG_CONFIG_PATH    # registered
+        export PKG_CONFIG_LIBDIR=""   # not registered
     fi
 }