diff --git a/src/gmpy2_binary.c b/src/gmpy2_binary.c
index ce50501d..9789b1a5 100644
--- a/src/gmpy2_binary.c
+++ b/src/gmpy2_binary.c
@@ -476,6 +476,7 @@ GMPy_MPFR_To_Binary(MPFR_Object *self)
         /* Only need to save the precision. */
         size += sizesize;
         TEMP_ALLOC(buffer, size);
+        memset(buffer, 0, size);
         buffer[0] = 0x04;
 
         /* Set to all 0 since we are special. */
@@ -510,6 +511,7 @@ GMPy_MPFR_To_Binary(MPFR_Object *self)
     /* Now process all actual numbers. */
     size += (2 * sizesize) + (sizemant * (mp_bits_per_limb >> 3));
     TEMP_ALLOC(buffer, size);
+    memset(buffer, 0, size);
     buffer[0] = 0x04;
 
     /* Set bit 0 to 1 since we are an actual number. */