diff --git a/testhal/STM32/SDIO/main.c b/testhal/STM32/SDIO/main.c
index 075af2cc3..8c5452ed7 100644
--- a/testhal/STM32/SDIO/main.c
+++ b/testhal/STM32/SDIO/main.c
@@ -28,7 +28,7 @@ static const SDCConfig sdccfg = {
   0
 };
 
-static uint8_t buf[SDC_BLOCK_SIZE * 2];
+static uint8_t blkbuf[SDC_BLOCK_SIZE * 4];
 
 /*
  * Application entry point.
@@ -53,15 +53,18 @@ int main(void) {
     int i;
     /* Repeated multiple reads.*/
     for (i = 0; i < 5000; i++) {
-      if (sdcRead(&SDCD1, 0, buf, 2))
+      if (sdcRead(&SDCD1, 0, blkbuf, 4))
+        chSysHalt();
+    }
+    /* Repeated multiple write.*/
+    for (i = 0; i < 100; i++) {
+      if (sdcRead(&SDCD1, 0x10000, blkbuf, 4))
+        chSysHalt();
+      if (sdcWrite(&SDCD1, 0x10000, blkbuf, 4))
+        chSysHalt();
+      if (sdcWrite(&SDCD1, 0x10000, blkbuf, 4))
         chSysHalt();
     }
-    if (sdcRead(&SDCD1, 0x10000, buf, 2))
-      chSysHalt();
-    if (sdcWrite(&SDCD1, 0x10000, buf, 2))
-      chSysHalt();
-    if (sdcRead(&SDCD1, 0x10000, buf, 2))
-      chSysHalt();
     if (sdcDisconnect(&SDCD1))
       chSysHalt();
   }