diff --git a/libc/utils/FPUtil/x86_64/FEnv.h b/libc/utils/FPUtil/x86_64/FEnv.h
--- a/libc/utils/FPUtil/x86_64/FEnv.h
+++ b/libc/utils/FPUtil/x86_64/FEnv.h
@@ -290,11 +290,12 @@
     return 1; // To indicate failure
   }
 
-  uint16_t x87Value = bitValue << internal::X87RoundingControlBitPosition;
+  uint16_t x87Value = static_cast<uint16_t>(
+      bitValue << internal::X87RoundingControlBitPosition);
   uint16_t x87Control = internal::getX87ControlWord();
-  x87Control =
+  x87Control = static_cast<uint16_t>(
       (x87Control & ~(0x3 << internal::X87RoundingControlBitPosition)) |
-      x87Value;
+      x87Value);
   internal::writeX87ControlWord(x87Control);
 
   uint32_t mxcsrValue = bitValue << internal::MXCSRRoundingControlBitPosition;