diff --git a/src/core/strtod.c b/src/core/strtod.c
index 78f9c8f0..9cfe09f8 100644
--- a/src/core/strtod.c
+++ b/src/core/strtod.c
@@ -208,9 +208,9 @@ static double convert(
 
     /* Approximate exponent in base 2 of mant and exponent. This should get us a good estimate of the final size of the
      * number, within * 2^32 or so. */
-    int32_t mant_exp2_approx = mant->n * 32 + 16;
-    int32_t exp_exp2_approx = (int32_t)(floor(log2(base) * exponent));
-    int32_t exp2_approx = mant_exp2_approx + exp_exp2_approx;
+    int64_t mant_exp2_approx = mant->n * 32 + 16;
+    int64_t exp_exp2_approx = (int64_t)(floor(log2(base) * exponent));
+    int64_t exp2_approx = mant_exp2_approx + exp_exp2_approx;
 
     /* Short circuit zero, huge, and small numbers. We use the exponent range of valid IEEE754 doubles (-1022, 1023)
      * with a healthy buffer to allow for inaccuracies in the approximation and denormailzed numbers. */
diff --git a/test/suite8.janet b/test/suite8.janet
index 591427ee..3a982f08 100644
--- a/test/suite8.janet
+++ b/test/suite8.janet
@@ -241,4 +241,7 @@ neldb\0\0\0\xD8\x05printG\x01\0\xDE\xDE\xDE'\x03\0marshal_tes/\x02
 (assert (nil? (first @"")) "in vs get 1")
 (assert (nil? (last @"")) "in vs get 1")
 
+# For undefined behavior sanitizer
+0xf&1fffFFFF
+
 (end-suite)