diff --git a/nimble/drivers/nrf51/src/ble_phy.c b/nimble/drivers/nrf51/src/ble_phy.c
index baa0208f2..1ce3ed923 100644
--- a/nimble/drivers/nrf51/src/ble_phy.c
+++ b/nimble/drivers/nrf51/src/ble_phy.c
@@ -210,6 +210,7 @@ ble_phy_rxpdu_copy(uint8_t *dptr, struct os_mbuf *rxpdu)
     uint32_t rem_len;
     uint32_t copy_len;
     uint32_t block_len;
+    uint32_t block_rem_len;
     void *dst;
     void *src;
     struct os_mbuf * om;
@@ -234,12 +235,14 @@ ble_phy_rxpdu_copy(uint8_t *dptr, struct os_mbuf *rxpdu)
          * Always copy blocks of length aligned to word size, only last mbuf
          * will have remaining non-word size bytes appended.
          */
+        block_rem_len = copy_len;
         copy_len = min(copy_len, rem_len);
         copy_len &= ~3;
 
         dst = om->om_data;
         om->om_len = copy_len;
         rem_len -= copy_len;
+        block_rem_len -= copy_len;
 
         __asm__ volatile (".syntax unified              \n"
                           "   mov  r4, %[len]           \n"
@@ -250,13 +253,13 @@ ble_phy_rxpdu_copy(uint8_t *dptr, struct os_mbuf *rxpdu)
                           "   bpl  1b                   \n"
                           "   adds %[src], %[src], r4   \n"
                           "   adds %[dst], %[dst], r4   \n"
-                          : [dst] "+r" (dst), [src] "+r" (src),
-                            [len] "+r" (copy_len)
+                          : [dst] "+l" (dst), [src] "+l" (src),
+                            [len] "+l" (copy_len)
                           :
                           : "r3", "r4", "memory"
                          );
 
-        if (rem_len < 4) {
+        if ((rem_len < 4) && (block_rem_len >= rem_len)) {
             break;
         }
 
@@ -273,8 +276,8 @@ ble_phy_rxpdu_copy(uint8_t *dptr, struct os_mbuf *rxpdu)
                       "   strb r3, [%[dst], %[len]] \n"
                       "2: subs %[len], #1           \n"
                       "   bpl  1b                   \n"
-                      : [len] "+r" (rem_len)
-                      : [dst] "r" (dst), [src] "r" (src)
+                      : [len] "+l" (rem_len)
+                      : [dst] "l" (dst), [src] "l" (src)
                       : "r3", "memory"
                      );
 
diff --git a/nimble/drivers/nrf52/src/ble_phy.c b/nimble/drivers/nrf52/src/ble_phy.c
index e49c7a180..7a499fd98 100644
--- a/nimble/drivers/nrf52/src/ble_phy.c
+++ b/nimble/drivers/nrf52/src/ble_phy.c
@@ -400,6 +400,7 @@ ble_phy_rxpdu_copy(uint8_t *dptr, struct os_mbuf *rxpdu)
     uint32_t rem_len;
     uint32_t copy_len;
     uint32_t block_len;
+    uint32_t block_rem_len;
     void *dst;
     void *src;
     struct os_mbuf * om;
@@ -424,12 +425,14 @@ ble_phy_rxpdu_copy(uint8_t *dptr, struct os_mbuf *rxpdu)
          * Always copy blocks of length aligned to word size, only last mbuf
          * will have remaining non-word size bytes appended.
          */
+        block_rem_len = copy_len;
         copy_len = min(copy_len, rem_len);
         copy_len &= ~3;
 
         dst = om->om_data;
         om->om_len = copy_len;
         rem_len -= copy_len;
+        block_rem_len -= copy_len;
 
         __asm__ volatile (".syntax unified              \n"
                           "   mov  r4, %[len]           \n"
@@ -446,7 +449,7 @@ ble_phy_rxpdu_copy(uint8_t *dptr, struct os_mbuf *rxpdu)
                           : "r3", "r4", "memory"
                          );
 
-        if (rem_len < 4) {
+        if ((rem_len < 4) && (block_rem_len >= rem_len)) {
             break;
         }