diff --git a/compiler/rustc_errors/src/diagnostic_builder.rs b/compiler/rustc_errors/src/diagnostic_builder.rs
index e72791d89a292..3789cdaf354aa 100644
--- a/compiler/rustc_errors/src/diagnostic_builder.rs
+++ b/compiler/rustc_errors/src/diagnostic_builder.rs
@@ -266,8 +266,7 @@ impl<'a, G: EmissionGuarantee> DiagnosticBuilder<'a, G> {
     /// Converts the builder to a `Diagnostic` for later emission,
     /// unless dcx has disabled such buffering.
     pub fn into_diagnostic(mut self) -> Option<(Diagnostic, &'a DiagCtxt)> {
-        let flags = self.dcx.inner.lock().flags;
-        if flags.dont_buffer_diagnostics || flags.treat_err_as_bug.is_some() {
+        if self.dcx.inner.lock().flags.treat_err_as_bug.is_some() {
             self.emit();
             return None;
         }
diff --git a/compiler/rustc_errors/src/lib.rs b/compiler/rustc_errors/src/lib.rs
index b97ec02675a60..76b7e0d79a98c 100644
--- a/compiler/rustc_errors/src/lib.rs
+++ b/compiler/rustc_errors/src/lib.rs
@@ -524,9 +524,6 @@ pub struct DiagCtxtFlags {
     /// If Some, the Nth error-level diagnostic is upgraded to bug-level.
     /// (rustc: see `-Z treat-err-as-bug`)
     pub treat_err_as_bug: Option<NonZeroUsize>,
-    /// If true, immediately emit diagnostics that would otherwise be buffered.
-    /// (rustc: see `-Z dont-buffer-diagnostics` and `-Z treat-err-as-bug`)
-    pub dont_buffer_diagnostics: bool,
     /// Show macro backtraces.
     /// (rustc: see `-Z macro-backtrace`)
     pub macro_backtrace: bool,
diff --git a/compiler/rustc_interface/src/tests.rs b/compiler/rustc_interface/src/tests.rs
index f3f59b05682db..444e3700cf772 100644
--- a/compiler/rustc_interface/src/tests.rs
+++ b/compiler/rustc_interface/src/tests.rs
@@ -659,7 +659,6 @@ fn test_unstable_options_tracking_hash() {
     // tidy-alphabetical-start
     untracked!(assert_incr_state, Some(String::from("loaded")));
     untracked!(deduplicate_diagnostics, false);
-    untracked!(dont_buffer_diagnostics, true);
     untracked!(dump_dep_graph, true);
     untracked!(dump_mir, Some(String::from("abc")));
     untracked!(dump_mir_dataflow, true);
diff --git a/compiler/rustc_session/src/config.rs b/compiler/rustc_session/src/config.rs
index 12d8293ecd2f6..61796d7a6cafc 100644
--- a/compiler/rustc_session/src/config.rs
+++ b/compiler/rustc_session/src/config.rs
@@ -1146,7 +1146,6 @@ impl UnstableOptions {
         DiagCtxtFlags {
             can_emit_warnings,
             treat_err_as_bug: self.treat_err_as_bug,
-            dont_buffer_diagnostics: self.dont_buffer_diagnostics,
             macro_backtrace: self.macro_backtrace,
             deduplicate_diagnostics: self.deduplicate_diagnostics,
             track_diagnostics: self.track_diagnostics,
diff --git a/compiler/rustc_session/src/options.rs b/compiler/rustc_session/src/options.rs
index 9c1c1c491b9b7..772c6df2e2d1f 100644
--- a/compiler/rustc_session/src/options.rs
+++ b/compiler/rustc_session/src/options.rs
@@ -1553,9 +1553,6 @@ options! {
     dep_info_omit_d_target: bool = (false, parse_bool, [TRACKED],
         "in dep-info output, omit targets for tracking dependencies of the dep-info files \
         themselves (default: no)"),
-    dont_buffer_diagnostics: bool = (false, parse_bool, [UNTRACKED],
-        "emit diagnostics rather than buffering (breaks NLL error downgrading, sorting) \
-        (default: no)"),
     dual_proc_macros: bool = (false, parse_bool, [TRACKED],
         "load proc macros for both target and host, but only link to the target (default: no)"),
     dump_dep_graph: bool = (false, parse_bool, [UNTRACKED],