diff --git a/os/hal/ports/STM32/LLD/USARTv2/hal_sio_lld.c b/os/hal/ports/STM32/LLD/USARTv2/hal_sio_lld.c
index fcc8543f8..49f547dfe 100644
--- a/os/hal/ports/STM32/LLD/USARTv2/hal_sio_lld.c
+++ b/os/hal/ports/STM32/LLD/USARTv2/hal_sio_lld.c
@@ -586,7 +586,7 @@ size_t sio_lld_read(SIODriver *siop, uint8_t *buffer, size_t n) {
     }
 
     /* Buffer filled condition.*/
-    if (rd > n) {
+    if (rd >= n) {
       break;
     }
 
diff --git a/os/hal/ports/STM32/LLD/USARTv3/hal_sio_lld.c b/os/hal/ports/STM32/LLD/USARTv3/hal_sio_lld.c
index ce4af1001..2604c333e 100644
--- a/os/hal/ports/STM32/LLD/USARTv3/hal_sio_lld.c
+++ b/os/hal/ports/STM32/LLD/USARTv3/hal_sio_lld.c
@@ -594,7 +594,7 @@ size_t sio_lld_read(SIODriver *siop, uint8_t *buffer, size_t n) {
     }
 
     /* Buffer filled condition.*/
-    if (rd > n) {
+    if (rd >= n) {
       break;
     }
 
diff --git a/readme.txt b/readme.txt
index f232e5589..6e8c3a975 100644
--- a/readme.txt
+++ b/readme.txt
@@ -120,6 +120,8 @@
 - NEW: On STM32WBxx added a check on STM32_LSI_ENABLE required by IWDG.
 - NEW: Added SPIv2 support also to STM32WB and STM32WL.
 - FIX: Reverted bug #1100 (backported to 20.3.5)(backported to 21.11.2).
+- FIX: Fixed wrong condition in STM32 sio_lld_read() function (bug #1219)
+       (backported to 20.3.5)(backported to 21.11.2).
 - FIX: Fixed clock re-initialization problem in STM32 USARTv2 and USARTv3
        drivers (bug #1217)(backported to 21.11.2).
 - FIX: Fixed assertion on initialization of STM32H7xx (bug #1216)