diff --git a/ffi/src/ffi/extra/json_parser.cc b/ffi/src/ffi/extra/json_parser.cc
index 3107e4ddf1ad..8bd372699dad 100644
--- a/ffi/src/ffi/extra/json_parser.cc
+++ b/ffi/src/ffi/extra/json_parser.cc
@@ -298,8 +298,12 @@ class JSONParserContext {
  private:
   static double FastMathSafePosInf() {
 #ifdef __FAST_MATH__
-    const uint64_t inf_bits = 0x7FF0000000000000ULL;
-    return *reinterpret_cast<const double*>(&inf_bits);
+    union {
+      uint64_t from;
+      double to;
+    } u;
+    u.from = 0x7FF0000000000000ULL;  // write "from", read "to"
+    return u.to;
 #else
     return std::numeric_limits<double>::infinity();
 #endif
@@ -307,8 +311,12 @@ class JSONParserContext {
 
   static double FastMathSafeNegInf() {
 #ifdef __FAST_MATH__
-    const uint64_t inf_bits = 0xFFF0000000000000ULL;
-    return *reinterpret_cast<const double*>(&inf_bits);
+    union {
+      uint64_t from;
+      double to;
+    } u;
+    u.from = 0xFFF0000000000000ULL;  // write "from", read "to"
+    return u.to;
 #else
     return -std::numeric_limits<double>::infinity();
 #endif
@@ -316,8 +324,12 @@ class JSONParserContext {
 
   static double FastMathSafeNaN() {
 #ifdef __FAST_MATH__
-    const uint64_t nan_bits = 0x7FF8000000000000ULL;
-    return *reinterpret_cast<const double*>(&nan_bits);
+    union {
+      uint64_t from;
+      double to;
+    } u;
+    u.from = 0x7FF8000000000000ULL;  // write "from", read "to"
+    return u.to;
 #else
     return std::numeric_limits<double>::quiet_NaN();
 #endif
diff --git a/ffi/src/ffi/extra/json_writer.cc b/ffi/src/ffi/extra/json_writer.cc
index 81d321d9a754..c2cd3f2f36d3 100644
--- a/ffi/src/ffi/extra/json_writer.cc
+++ b/ffi/src/ffi/extra/json_writer.cc
@@ -66,7 +66,12 @@ class JSONWriter {
     // IEEE 754 standard: https://en.wikipedia.org/wiki/IEEE_754
     // NaN is encoded as all 1s in the exponent and non-zero in the mantissa
     static_assert(sizeof(double) == sizeof(uint64_t), "Unexpected double size");
-    uint64_t bits = *reinterpret_cast<const uint64_t*>(&x);
+    union {
+      double from;
+      uint64_t to;
+    } u;
+    u.from = x;  // write "from", read "to"
+    uint64_t bits = u.to;
     uint64_t exponent = (bits >> 52) & 0x7FF;
     uint64_t mantissa = bits & 0xFFFFFFFFFFFFFull;
     return (exponent == 0x7FF) && (mantissa != 0);
@@ -81,7 +86,12 @@ class JSONWriter {
     // IEEE 754 standard: https://en.wikipedia.org/wiki/IEEE_754
     // Inf is encoded as all 1s in the exponent and zero in the mantissa
     static_assert(sizeof(double) == sizeof(uint64_t), "Unexpected double size");
-    uint64_t bits = *reinterpret_cast<const uint64_t*>(&x);
+    union {
+      double from;
+      uint64_t to;
+    } u;
+    u.from = x;  // write "from", read "to"
+    uint64_t bits = u.to;
     uint64_t exponent = (bits >> 52) & 0x7FF;
     uint64_t mantissa = bits & 0xFFFFFFFFFFFFFull;
     // inf is encoded as all 1s in the exponent and zero in the mantissa