diff --git a/src/data/set.cpp b/src/data/set.cpp
index 28fcbbf4..39ab8d4f 100644
--- a/src/data/set.cpp
+++ b/src/data/set.cpp
@@ -208,7 +208,9 @@ void Set::reflect_cards<Writer> (Writer& tag) {
 	} else {
 		set<String> used;
 		FOR_EACH(card, cards) {
-			String filename = normalize_internal_filename(clean_filename(card->identification()));
+			// pick a unique filename for this card
+			// can't use Package::newFileName, because then we get conflicts with the previous save of the same card
+			String filename = _("card ") + normalize_internal_filename(clean_filename(card->identification()));
 			String full_name = filename;
 			int i = 0;
 
diff --git a/src/util/file_utils.cpp b/src/util/file_utils.cpp
index 1fa1f9aa..db8bed05 100644
--- a/src/util/file_utils.cpp
+++ b/src/util/file_utils.cpp
@@ -42,11 +42,18 @@ bool is_filename_char(Char c) {
 
 String clean_filename(const String& name) {
 	String clean;
+	// allow only valid characters, and remove leading whitespace
+	bool start = true;
 	FOR_EACH_CONST(c, name) {
-		if (is_filename_char(c)) {
+		if (is_filename_char(c) && !(start && c == _(' '))) {
+			start = false;
 			clean += c;
 		}
 	}
+	// remove trailing whitespace
+	while (!clean.empty() && clean[clean.size()-1] == _(' ')) {
+		clean.resize(clean.size()-1);
+	}
 	if (clean.empty() || starts_with(clean, _("."))) {
 		clean = _("no-name") + clean;
 	}