diff --git a/common_arm/usb_cdc.c b/common_arm/usb_cdc.c
index cb2d0c64a..37ecd0497 100644
--- a/common_arm/usb_cdc.c
+++ b/common_arm/usb_cdc.c
@@ -797,7 +797,7 @@ int usb_write(const uint8_t *data, const size_t len) {
         while (pUdp->UDP_CSR[AT91C_EP_IN] & AT91C_UDP_TXCOMP) {};
 
         UDP_SET_EP_FLAGS(AT91C_EP_IN, AT91C_UDP_TXPKTRDY);
-        while (pUdp->UDP_CSR[AT91C_EP_IN] & AT91C_UDP_TXPKTRDY) {};
+        while (!(pUdp->UDP_CSR[AT91C_EP_IN] & AT91C_UDP_TXPKTRDY)) {};
     }
 
     // Wait for the end of transfer
@@ -812,7 +812,7 @@ int usb_write(const uint8_t *data, const size_t len) {
     if (len % AT91C_EP_IN_SIZE == 0) {
 
         UDP_SET_EP_FLAGS(AT91C_EP_IN, AT91C_UDP_TXPKTRDY);
-        while (!(pUdp->UDP_CSR[AT91C_EP_IN] & AT91C_UDP_TXCOMP)) {};
+        while (!(pUdp->UDP_CSR[AT91C_EP_IN] & AT91C_UDP_TXPKTRDY)) {};
 
         UDP_CLEAR_EP_FLAGS(AT91C_EP_IN, AT91C_UDP_TXCOMP);
         while (pUdp->UDP_CSR[AT91C_EP_IN] & AT91C_UDP_TXCOMP) {};