diff --git a/scumm/script_v6he.cpp b/scumm/script_v6he.cpp
index f8ed2965dfa..79290d53f01 100644
--- a/scumm/script_v6he.cpp
+++ b/scumm/script_v6he.cpp
@@ -1031,6 +1031,10 @@ void ScummEngine_v6he::o6_readFile() {
 	int32 size = pop();
 	int slot = pop();
 
+	// Fatty Bear uses positive values
+	if (_gameId == GID_FBEAR)
+		size = -size;
+
 	if (size == -2) {
 		push(_hFileTable[slot].readUint16LE());
 	} else if (size == -1) {
@@ -1053,6 +1057,10 @@ void ScummEngine_v6he::o6_writeFile() {
 	int16 resID = pop();
 	int slot = pop();
 
+	// Fatty Bear uses positive values
+	if (_gameId == GID_FBEAR)
+		size = -size;
+
 	if (size == -2) {
 		_hFileTable[slot].writeUint16LE(resID);
 	} else if (size == -1) {