diff --git a/Source/Core/Core/HW/GCMemcard/GCMemcard.cpp b/Source/Core/Core/HW/GCMemcard/GCMemcard.cpp
index f610243238..adccd920fa 100644
--- a/Source/Core/Core/HW/GCMemcard/GCMemcard.cpp
+++ b/Source/Core/Core/HW/GCMemcard/GCMemcard.cpp
@@ -249,8 +249,11 @@ std::pair<GCMemcardErrorCode, std::optional<GCMemcard>> GCMemcard::Open(std::str
   error_code |= bat_block_1_error_code;
 
   // select the in-use Dir and BAT blocks based on update counter
-  // TODO: Is there a special case for wraparound after 65535 block updates, or is it assumed that
-  // the hardware fails long before that anyway?
+
+  // These are compared as signed values by the GC BIOS. There is no protection against overflow, so
+  // if one block is MAX_VAL and the other is MIN_VAL it still picks the MAX_VAL one as the active
+  // one, even if that results in a corrupted memory card.
+  // TODO: We could try to be smarter about this to rescue seemingly-corrupted cards.
 
   if (card.m_directory_blocks[0].m_update_counter >= card.m_directory_blocks[1].m_update_counter)
     card.m_active_directory = 0;
diff --git a/Source/Core/Core/HW/GCMemcard/GCMemcard.h b/Source/Core/Core/HW/GCMemcard/GCMemcard.h
index 8855a493de..50d0913787 100644
--- a/Source/Core/Core/HW/GCMemcard/GCMemcard.h
+++ b/Source/Core/Core/HW/GCMemcard/GCMemcard.h
@@ -311,8 +311,7 @@ struct Directory
   std::array<u8, 0x3a> m_padding;
 
   // 2 bytes at 0x1ffa: Update Counter
-  // TODO: What happens if this overflows? Is there a special case for preferring 0 over max value?
-  Common::BigEndianValue<u16> m_update_counter;
+  Common::BigEndianValue<s16> m_update_counter;
 
   // 2 bytes at 0x1ffc: Additive Checksum
   u16 m_checksum;
@@ -343,7 +342,7 @@ struct BlockAlloc
   u16 m_checksum_inv;
 
   // 2 bytes at 0x0004: Update Counter
-  Common::BigEndianValue<u16> m_update_counter;
+  Common::BigEndianValue<s16> m_update_counter;
 
   // 2 bytes at 0x0006: Free Blocks
   Common::BigEndianValue<u16> m_free_blocks;