diff --git a/armsrc/BigBuf.c b/armsrc/BigBuf.c
index 4f99ae756..0949558f3 100644
--- a/armsrc/BigBuf.c
+++ b/armsrc/BigBuf.c
@@ -92,9 +92,9 @@ uint32_t BigBuf_get_size(void) {
 // get the address of the emulator memory. Allocate part of Bigbuf for it, if not yet done
 uint8_t *BigBuf_get_EM_addr(void) {
     // not yet allocated
-    if (emulator_memory == NULL)
-        emulator_memory = BigBuf_malloc(CARD_MEMORY_SIZE);
-
+    if (emulator_memory == NULL) {
+        emulator_memory = BigBuf_calloc(CARD_MEMORY_SIZE);
+    }
     return emulator_memory;
 }
 
@@ -366,8 +366,9 @@ void tosend_stuffbit(int b) {
 }
 
 dmabuf16_t *get_dma16(void) {
-    if (dma_16.buf == NULL)
+    if (dma_16.buf == NULL) {
         dma_16.buf = (uint16_t *)BigBuf_malloc(DMA_BUFFER_SIZE * sizeof(uint16_t));
+    }
 
     return &dma_16;
 }
diff --git a/armsrc/BigBuf.h b/armsrc/BigBuf.h
index e496ce2f7..7eb8fa2ce 100644
--- a/armsrc/BigBuf.h
+++ b/armsrc/BigBuf.h
@@ -26,7 +26,7 @@
 #define MAX_MIFARE_FRAME_SIZE   18  // biggest Mifare frame is answer to a read (one block = 16 Bytes) + 2 Bytes CRC
 #define MAX_MIFARE_PARITY_SIZE  3   // need 18 parity bits for the 18 Byte above. 3 Bytes are enough to store these
 #define CARD_MEMORY_SIZE        4096
-#define DMA_BUFFER_SIZE         512
+#define DMA_BUFFER_SIZE         (512 + 256)
 
 // 8 data bits and 1 parity bit per payload byte, 1 correction bit, 1 SOC bit, 2 EOC bits
 #define TOSEND_BUFFER_SIZE (9 * MAX_FRAME_SIZE + 1 + 1 + 2)