diff --git a/engines/sci/engine/savegame.cpp b/engines/sci/engine/savegame.cpp
index a27b699dd1a..e67e4764a2d 100644
--- a/engines/sci/engine/savegame.cpp
+++ b/engines/sci/engine/savegame.cpp
@@ -568,7 +568,7 @@ void Script::saveLoadWithSerializer(Common::Serializer &s) {
 
 	s.skip(4, VER(14), VER(19));		// OBSOLETE: Used to be _numExports
 	s.skip(4, VER(14), VER(19));		// OBSOLETE: Used to be _numSynonyms
-	s.syncAsSint32LE(_lockers);
+	s.syncAsUint32LE(_lockers);
 
 	// Sync _objects. This is a hashmap, and we use the following on disk format:
 	// First we store the number of items in the hashmap, then we store each
diff --git a/engines/sci/engine/script.cpp b/engines/sci/engine/script.cpp
index a1ba52184d8..cbc91293530 100644
--- a/engines/sci/engine/script.cpp
+++ b/engines/sci/engine/script.cpp
@@ -841,6 +841,21 @@ void Script::relocateSci3(const SegmentId segmentId) {
 
 void Script::incrementLockers() {
 	assert(!_markedAsDeleted);
+	if (_lockers == 0xffffffff) {
+		// FIXME
+		// The locker on system scripts, most notably script 999, increases throughout
+		// the game and can eventually overflow, causing script 999 to be unloaded
+		// and crash. We have been provided QFG1 SCI0 save games where this occurred
+		// within hours of play over the course of three days. Debugging shows that
+		// this value increases rapidly, for example: on every `class Event` opcode
+		// during input polling, or when our kAnimate code calls `doit` on objects.
+		// Until this is fixed properly, log these overflow attempts and lower the
+		// counter so that the warnings continue without flooding the log.
+		// At the point where a resource usage counter reaches the billions, its value
+		// no longer has meaning, so the important thing for now is that it not crash.
+		warning("script %d locker maximum reached, resetting", _nr);
+		_lockers = 0x80000000;
+	}
 	_lockers++;
 }
 
@@ -849,11 +864,11 @@ void Script::decrementLockers() {
 		_lockers--;
 }
 
-int Script::getLockers() const {
+uint Script::getLockers() const {
 	return _lockers;
 }
 
-void Script::setLockers(int lockers) {
+void Script::setLockers(uint lockers) {
 	assert(lockers == 0 || !_markedAsDeleted);
 	_lockers = lockers;
 }
diff --git a/engines/sci/engine/script.h b/engines/sci/engine/script.h
index 4f9e086daf1..13c441d071c 100644
--- a/engines/sci/engine/script.h
+++ b/engines/sci/engine/script.h
@@ -75,7 +75,7 @@ private:
 	SciSpan<byte> _script; /**< Script size includes alignment byte */
 	SciSpan<byte> _heap; /**< Start of heap if SCI1.1, NULL otherwise */
 
-	int _lockers; /**< Number of classes and objects that require this script */
+	uint _lockers; /**< Number of classes and objects that require this script */
 
 	SciSpan<const uint16> _exports; /**< Exports block or 0 if not present */
 	uint16 _numExports; /**< Number of export entries */
@@ -197,10 +197,10 @@ public:
 	 * Retrieves the number of locks held on this script.
 	 * @return the number of locks held on the previously identified script
 	 */
-	int getLockers() const;
+	uint getLockers() const;
 
 	/** Sets the number of locks held on this script. */
-	void setLockers(int lockers);
+	void setLockers(uint lockers);
 
 	/**
 	 * Retrieves the offset of the export table in the script