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
@@ -48,6 +48,8 @@
   static constexpr uint16_t Inexact = 0x20;
 };
 
+static constexpr uint16_t ExceptionSummaryStatusBit = 0x80;
+
 // The exception control bits occupy six bits, one bit for each exception.
 // In the x87 control word, they occupy the first 6 bits. In the MXCSR
 // register, they occupy bits 7 to 12.
@@ -194,6 +196,14 @@
       (statusValue & internal::getMXCSR()));
 }
 
+// This function returns a bitmap of which exceptions selected are enabled.
+static inline int isEnabled(int excepts) {
+  uint16_t x87CW = internal::getX87ControlWord();
+  return excepts & (~x87CW);
+  // The exceptions are enabled if the bit is zero (unmasked),
+  // so that is why the negation before the & operation.
+}
+
 static inline int raiseExcept(int excepts) {
   uint16_t statusValue = internal::getStatusValueForExcept(excepts);
 
@@ -214,6 +224,9 @@
     internal::X87State state;
     internal::getX87State(state);
     state.StatusWord |= internal::ExceptionFlags::Invalid;
+    if (isEnabled(internal::ExceptionFlags::Invalid)) {
+      state.StatusWord |= internal::ExceptionSummaryStatusBit;
+    }
     internal::writeX87State(state);
     internal::fwait();
   }
@@ -221,6 +234,9 @@
     internal::X87State state;
     internal::getX87State(state);
     state.StatusWord |= internal::ExceptionFlags::DivByZero;
+    if (isEnabled(internal::ExceptionFlags::DivByZero)) {
+      state.StatusWord |= internal::ExceptionSummaryStatusBit;
+    }
     internal::writeX87State(state);
     internal::fwait();
   }
@@ -228,6 +244,9 @@
     internal::X87State state;
     internal::getX87State(state);
     state.StatusWord |= internal::ExceptionFlags::Overflow;
+    if (isEnabled(internal::ExceptionFlags::Overflow)) {
+      state.StatusWord |= internal::ExceptionSummaryStatusBit;
+    }
     internal::writeX87State(state);
     internal::fwait();
   }
@@ -235,6 +254,9 @@
     internal::X87State state;
     internal::getX87State(state);
     state.StatusWord |= internal::ExceptionFlags::Underflow;
+    if (isEnabled(internal::ExceptionFlags::Underflow)) {
+      state.StatusWord |= internal::ExceptionSummaryStatusBit;
+    }
     internal::writeX87State(state);
     internal::fwait();
   }
@@ -242,6 +264,9 @@
     internal::X87State state;
     internal::getX87State(state);
     state.StatusWord |= internal::ExceptionFlags::Inexact;
+    if (isEnabled(internal::ExceptionFlags::Inexact)) {
+      state.StatusWord |= internal::ExceptionSummaryStatusBit;
+    }
     internal::writeX87State(state);
     internal::fwait();
   }