diff --git a/wolfcrypt/src/tfm.c b/wolfcrypt/src/tfm.c
index f7fd26ed0..155695936 100644
--- a/wolfcrypt/src/tfm.c
+++ b/wolfcrypt/src/tfm.c
@@ -3581,7 +3581,8 @@ int fp_read_unsigned_bin(fp_int *a, const unsigned char *b, int c)
 #error Both LITTLE_ENDIAN_ORDER and BIG_ENDIAN_ORDER defined.
 #endif
 
-#if (defined(LITTLE_ENDIAN_ORDER) || defined(BIG_ENDIAN_ORDER))
+#if (defined(LITTLE_ENDIAN_ORDER) || defined(BIG_ENDIAN_ORDER)) && \
+    (defined(FP_32BIT) || defined(FP_64BIT))
 #ifdef FP_32BIT
   /* If we know the endianness of this architecture, and we're using
      32-bit fp_digits, we can optimize this */
@@ -3589,7 +3590,6 @@ int fp_read_unsigned_bin(fp_int *a, const unsigned char *b, int c)
      unsigned char *pd = (unsigned char *)a->dp;
 
      a->used = (c + sizeof(fp_digit) - 1)/sizeof(fp_digit);
-     /* read the bytes in */
 #ifdef BIG_ENDIAN_ORDER
      {
        /* Use Duff's device to unroll the loop. */
@@ -3604,6 +3604,7 @@ int fp_read_unsigned_bin(fp_int *a, const unsigned char *b, int c)
        }
      }
 #else
+     /* read the bytes in one at a time. */
      for (c -= 1; c >= 0; c -= 1) {
        pd[c] = *b++;
      }
@@ -3616,7 +3617,6 @@ int fp_read_unsigned_bin(fp_int *a, const unsigned char *b, int c)
      unsigned char *pd = (unsigned char *)a->dp;
 
      a->used = (c + sizeof(fp_digit) - 1)/sizeof(fp_digit);
-     /* read the bytes in */
 #ifdef BIG_ENDIAN_ORDER
      {
        /* Use Duff's device to unroll the loop. */
@@ -3635,6 +3635,7 @@ int fp_read_unsigned_bin(fp_int *a, const unsigned char *b, int c)
        }
      }
 #else
+     /* read the bytes in one at a time. */
      for (c -= 1; c >= 0; c -= 1) {
        pd[c] = *b++;
      }
@@ -3642,7 +3643,7 @@ int fp_read_unsigned_bin(fp_int *a, const unsigned char *b, int c)
   }
 #endif
 #else
-  /* read the bytes in */
+  /* read the bytes in one at a time - unknown number of bits in digit */
   for (; c > 0; c--) {
      int err = fp_mul_2d (a, 8, a);
      if (err != FP_OKAY) {