diff --git a/include/rapidjson/internal/diyfp.h b/include/rapidjson/internal/diyfp.h
index 320d05d..0b098af 100644
--- a/include/rapidjson/internal/diyfp.h
+++ b/include/rapidjson/internal/diyfp.h
@@ -238,7 +238,7 @@ inline DiyFp GetCachedPower(int e, int* K) {
     //int k = static_cast<int>(ceil((-61 - e) * 0.30102999566398114)) + 374;
     double dk = (-61 - e) * 0.30102999566398114 + 347;  // dk must be positive, so can do ceiling in positive
     int k = static_cast<int>(dk);
-    if (k != dk)
+    if (dk - k > 0.0)
         k++;
 
     unsigned index = static_cast<unsigned>((k >> 3) + 1);
diff --git a/include/rapidjson/internal/dtoa.h b/include/rapidjson/internal/dtoa.h
index bf686b0..aec6bcd 100644
--- a/include/rapidjson/internal/dtoa.h
+++ b/include/rapidjson/internal/dtoa.h
@@ -193,8 +193,8 @@ inline char* Prettify(char* buffer, int length, int k) {
 }
 
 inline char* dtoa(double value, char* buffer) {
-    if (value == 0) {
-        Double d(value);
+    Double d(value);
+    if (d.IsZero()) {
         if (d.Sign())
             *buffer++ = '-';     // -0.0, Issue #289
         buffer[0] = '0';
diff --git a/include/rapidjson/internal/ieee754.h b/include/rapidjson/internal/ieee754.h
index 934cf19..0b9393e 100644
--- a/include/rapidjson/internal/ieee754.h
+++ b/include/rapidjson/internal/ieee754.h
@@ -49,6 +49,7 @@ public:
     bool IsNan() const { return (u & kExponentMask) == kExponentMask && Significand() != 0; }
     bool IsInf() const { return (u & kExponentMask) == kExponentMask && Significand() == 0; }
     bool IsNormal() const { return (u & kExponentMask) != 0 || Significand() == 0; }
+    bool IsZero() const { return (u & (kExponentMask | kSignificandMask)) == 0; }
 
     uint64_t IntegerSignificand() const { return IsNormal() ? Significand() | kHiddenBit : Significand(); }
     int IntegerExponent() const { return (IsNormal() ? Exponent() : kDenormalExponent) - kSignificandSize; }