diff --git a/src/hw_ostc3.c b/src/hw_ostc3.c
index 119af09..ff821c6 100644
--- a/src/hw_ostc3.c
+++ b/src/hw_ostc3.c
@@ -106,7 +106,7 @@ typedef struct hw_ostc3_device_t {
 	unsigned int firmware;
 	unsigned char fingerprint[5];
 	hw_ostc3_state_t state;
-	unsigned char cache[20];
+	unsigned char cache[244];
 	unsigned int available;
 	unsigned int offset;
 } hw_ostc3_device_t;