diff --git a/src/main/io/flashfs.c b/src/main/io/flashfs.c
index 429ffe8ad..bfc6007dd 100644
--- a/src/main/io/flashfs.c
+++ b/src/main/io/flashfs.c
@@ -481,7 +481,7 @@ int flashfsIdentifyStartOfFreeSpace()
         /* We can choose whatever power of 2 size we like, which determines how much wastage of free space we'll have
          * at the end of the last written data. But smaller blocksizes will require more searching.
          */
-        FREE_BLOCK_SIZE = 65536,
+        FREE_BLOCK_SIZE = 2048,
 
         /* We don't expect valid data to ever contain this many consecutive uint32_t's of all 1 bits: */
         FREE_BLOCK_TEST_SIZE_INTS = 4, // i.e. 16 bytes
@@ -493,16 +493,20 @@ int flashfsIdentifyStartOfFreeSpace()
         uint32_t ints[FREE_BLOCK_TEST_SIZE_INTS];
     } testBuffer;
 
-    int left = 0;
-    int right = flashfsGetSize() / FREE_BLOCK_SIZE;
-    int mid, result = right;
+    int left = 0; // Smallest block index in the search region
+    int right = flashfsGetSize() / FREE_BLOCK_SIZE; // One past the largest block index in the search region
+    int mid;
+    int result = right;
     int i;
     bool blockErased;
 
     while (left < right) {
         mid = (left + right) / 2;
 
-        m25p16_readBytes(mid * FREE_BLOCK_SIZE, testBuffer.bytes, FREE_BLOCK_TEST_SIZE_BYTES);
+        if (m25p16_readBytes(mid * FREE_BLOCK_SIZE, testBuffer.bytes, FREE_BLOCK_TEST_SIZE_BYTES) < FREE_BLOCK_TEST_SIZE_BYTES) {
+            // Unexpected timeout from flash, so bail early (reporting the device fuller than it really is)
+            break;
+        }
 
         // Checking the buffer 4 bytes at a time like this is probably faster than byte-by-byte, but I didn't benchmark it :)
         blockErased = true;