diff --git a/klamath/basic.py b/klamath/basic.py
index 7bbd00e..fd1b417 100644
--- a/klamath/basic.py
+++ b/klamath/basic.py
@@ -43,7 +43,7 @@ def decode_real8(nums: numpy.ndarray) -> numpy.ndarray:
     exp = (nums >> 56) & 0x7f
     mant = (nums & 0x00ff_ffff_ffff_ffff).astype(numpy.float64)
     mant[neg != 0] *= -1
-    return numpy.ldexp(mant, 4 * (exp - 64) - 56, dtype=numpy.float64)
+    return numpy.ldexp(mant, (4 * (exp - 64) - 56).astype(numpy.int64))
 
 
 def parse_real8(data: bytes) -> numpy.ndarray: