diff --git a/src/cn-encoder.c b/src/cn-encoder.c
index d8a4d49..9ea97ee 100644
--- a/src/cn-encoder.c
+++ b/src/cn-encoder.c
@@ -116,7 +116,7 @@ static void _write_positive(cn_write_state *ws, cn_cbor_type typ, uint64_t val)
 static void _write_double(cn_write_state *ws, double val)
 {
   float float_val = val;
-  if (float_val == val) {                /* 32 bits is enough and we aren't NaN */
+  if ((double)float_val == val) { /* 32 bits is enough and we aren't NaN */
     uint32_t be32;
     uint16_t be16, u16;
     union {