diff --git a/libc/config/windows/entrypoints.txt b/libc/config/windows/entrypoints.txt
--- a/libc/config/windows/entrypoints.txt
+++ b/libc/config/windows/entrypoints.txt
@@ -39,6 +39,39 @@
     libc.src.string.strtok
     libc.src.string.strtok_r
 )
+
+set(TARGET_LIBM_ENTRYPOINTS
+    # math.h entrypoints
+    libc.src.math.copysign
+    libc.src.math.copysignf
+    libc.src.math.copysignl
+    libc.src.math.fdimf
+    libc.src.math.fdim
+    libc.src.math.fdiml
+    libc.src.math.fmin
+    libc.src.math.fminf
+    libc.src.math.fminl
+    libc.src.math.fmax
+    libc.src.math.fmaxf
+    libc.src.math.fmaxl
+    libc.src.math.ilogb
+    libc.src.math.ilogbf
+    libc.src.math.ilogbl
+    libc.src.math.ldexp
+    libc.src.math.ldexpf
+    libc.src.math.ldexpl
+    libc.src.math.logb
+    libc.src.math.logbf
+    libc.src.math.logbl
+    libc.src.math.modf
+    libc.src.math.modff
+    libc.src.math.modfl
+    libc.src.math.nextafter
+    libc.src.math.nextafterf
+    libc.src.math.nextafterl
+)
+
 set(TARGET_LLVMLIBC_ENTRYPOINTS
   ${TARGET_LIBC_ENTRYPOINTS}
+  ${TARGET_LIBM_ENTRYPOINTS}
 )
diff --git a/libc/test/src/math/NextAfterTest.h b/libc/test/src/math/NextAfterTest.h
--- a/libc/test/src/math/NextAfterTest.h
+++ b/libc/test/src/math/NextAfterTest.h
@@ -22,12 +22,8 @@
   using MantissaWidth = __llvm_libc::fputil::MantissaWidth<T>;
   using UIntType = typename FPBits::UIntType;
 
-#if (defined(__x86_64__) || defined(__i386__))
   static constexpr int bitWidthOfType =
-      __llvm_libc::cpp::IsSame<T, long double>::Value ? 80 : (sizeof(T) * 8);
-#else
-  static constexpr int bitWidthOfType = sizeof(T) * 8;
-#endif
+      __llvm_libc::fputil::FloatProperties<T>::bitWidth;
 
   const T zero = T(FPBits::zero());
   const T negZero = T(FPBits::negZero());
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
@@ -91,12 +91,16 @@
   uint16_t StatusWord;
   uint16_t Unused2;
   // TODO: Elaborate the remaining 20 bytes as required.
+#if !(defined(_WIN32) || defined(_WIN64))
   uint32_t _[5];
+#endif
 };
 
 struct FPState {
   X87StateDescriptor X87Status;
+#if !(defined(_WIN32) || defined(_WIN64))
   uint32_t MXCSR;
+#endif
 };
 
 static_assert(
@@ -349,7 +353,9 @@
 static inline int getEnv(fenv_t *envp) {
   internal::FPState *state = reinterpret_cast<internal::FPState *>(envp);
   internal::getX87StateDescriptor(state->X87Status);
+#if !(defined(_WIN32) || defined(_WIN64))
   state->MXCSR = internal::getMXCSR();
+#endif
   return 0;
 }
 
@@ -357,7 +363,9 @@
   const internal::FPState *state =
       reinterpret_cast<const internal::FPState *>(envp);
   internal::writeX87StateDescriptor(state->X87Status);
+#if !(defined(_WIN32) || defined(_WIN64))
   internal::writeMXCSR(state->MXCSR);
+#endif
   return 0;
 }