diff --git a/wolfcrypt/src/tfm.c b/wolfcrypt/src/tfm.c
index 1a8050b20..970c3e9d7 100644
--- a/wolfcrypt/src/tfm.c
+++ b/wolfcrypt/src/tfm.c
@@ -1430,7 +1430,7 @@ int fp_invmod_mont_ct(fp_int *a, fp_int *b, fp_int *c, fp_digit mp)
   fp_int* pre;
 #endif
 
-  if ((a->used * 2 > FP_MAX_BITS) || (b->used * 2 > FP_MAX_BITS)) {
+  if ((a->used * 2 > FP_SIZE) || (b->used * 2 > FP_SIZE)) {
     return FP_VAL;
   }