diff --git a/wolfcrypt/src/tfm.c b/wolfcrypt/src/tfm.c
index 16468ff9f..18a6dc790 100644
--- a/wolfcrypt/src/tfm.c
+++ b/wolfcrypt/src/tfm.c
@@ -4802,6 +4802,9 @@ static int fp_read_radix_16(fp_int *a, const char *str)
       else
           return FP_VAL;
 
+      if (k >= FP_SIZE)
+          return FP_VAL;
+
       a->dp[k] |= ((fp_digit)ch) << j;
       j += 4;
       k += j == DIGIT_BIT;