diff --git a/libc/src/setjmp/x86_64/longjmp.cpp b/libc/src/setjmp/x86_64/longjmp.cpp
--- a/libc/src/setjmp/x86_64/longjmp.cpp
+++ b/libc/src/setjmp/x86_64/longjmp.cpp
@@ -29,6 +29,7 @@
   // |val| in rax. Note that this has to happen before we restore the registers
   // from values in |buf|. Otherwise, once rsp and rbp are updated, we cannot
   // read |val|.
+  val = val == 0 ? 1 : val;
   LIBC_INLINE_ASM("mov %1, %0\n\t" : "=r"(rax) : "m"(val) :);
   LIBC_INLINE_ASM("mov %1, %0\n\t" : "=r"(rbx) : "m"(buf->rbx) :);
   LIBC_INLINE_ASM("mov %1, %0\n\t" : "=r"(rbp) : "m"(buf->rbp) :);
diff --git a/libc/test/src/setjmp/setjmp_test.cpp b/libc/test/src/setjmp/setjmp_test.cpp
--- a/libc/test/src/setjmp/setjmp_test.cpp
+++ b/libc/test/src/setjmp/setjmp_test.cpp
@@ -28,3 +28,13 @@
   }
   ASSERT_EQ(n, MAX_LOOP + 1);
 }
+
+TEST(LlvmLibcSetJmpTest, SetAndJumpBackValOne) {
+  jmp_buf env;
+
+  int val = __llvm_libc::setjmp(env);
+  if (val == 0)
+    __llvm_libc::longjmp(env, val);
+
+  ASSERT_EQ(val, 1);
+}
\ No newline at end of file