diff --git a/tools/tpm/policy_create.c b/tools/tpm/policy_create.c
index 15b85555..b4115d90 100644
--- a/tools/tpm/policy_create.c
+++ b/tools/tpm/policy_create.c
@@ -54,7 +54,7 @@ int writeBin(const char* filename, const uint8_t*buf, word32 bufSz)
     XFILE fp = NULL;
     size_t fileSz = 0;
 
-    fp = XFOPEN(filename, "wt");
+    fp = XFOPEN(filename, "wb");
     if (fp != XBADFILE) {
         fileSz = XFWRITE(buf, 1, bufSz, fp);
         /* sanity check */
diff --git a/tools/tpm/policy_sign.c b/tools/tpm/policy_sign.c
index 2afe408a..e0ee352e 100644
--- a/tools/tpm/policy_sign.c
+++ b/tools/tpm/policy_sign.c
@@ -224,7 +224,7 @@ static int writeBin(const char* filename, const byte *buf, word32 bufSz)
     FILE *fp = NULL;
     size_t fileSz = 0;
 
-    fp = fopen(filename, "wt");
+    fp = fopen(filename, "wb");
     if (fp != NULL) {
         fileSz = fwrite(buf, 1, bufSz, fp);
         /* sanity check */