diff --git a/js/src/frontend/BytecodeCompiler.cpp b/js/src/frontend/BytecodeCompiler.cpp
index b014146f66cf..b72808efffb6 100644
--- a/js/src/frontend/BytecodeCompiler.cpp
+++ b/js/src/frontend/BytecodeCompiler.cpp
@@ -417,7 +417,7 @@ bool BytecodeCompiler::canLazilyParse() const {
   return options.canLazilyParse &&
          !cx->realm()->behaviors().disableLazyParsing() &&
          !cx->realm()->behaviors().discardSource() && !options.sourceIsLazy &&
-         !cx->lcovEnabled() &&
+         !coverage::IsLCovEnabled() &&
          // Disabled during record/replay. The replay debugger requires
          // scripts to be constructed in a consistent order, which might not
          // happen with lazy parsing.
diff --git a/js/src/gc/GC.cpp b/js/src/gc/GC.cpp
index a082a51cde80..4f0d40b1bdfe 100644
--- a/js/src/gc/GC.cpp
+++ b/js/src/gc/GC.cpp
@@ -8175,7 +8175,7 @@ void GCRuntime::mergeRealms(Realm* source, Realm* target) {
   atomMarking.adoptMarkedAtoms(target->zone(), source->zone());
 
   // Merge script name maps in the target realm's map.
-  if (rt->lcovOutput().isEnabled() && source->scriptNameMap) {
+  if (coverage::IsLCovEnabled() && source->scriptNameMap) {
     AutoEnterOOMUnsafeRegion oomUnsafe;
 
     if (!target->scriptNameMap) {
diff --git a/js/src/shell/js.cpp b/js/src/shell/js.cpp
index d3d6f857ffab..0403b4b5b1ce 100644
--- a/js/src/shell/js.cpp
+++ b/js/src/shell/js.cpp
@@ -10542,7 +10542,6 @@ static bool SetContextOptions(JSContext* cx, const OptionParser& op) {
   reportWarnings = op.getBoolOption('w');
   compileOnly = op.getBoolOption('c');
   printTiming = op.getBoolOption('b');
-  enableCodeCoverage = op.getBoolOption("code-coverage");
   enableDisassemblyDumps = op.getBoolOption('D');
   cx->runtime()->profilingScripts =
       enableCodeCoverage || enableDisassemblyDumps;
@@ -11228,6 +11227,11 @@ int main(int argc, char** argv, char** envp) {
     js::DisableExtraThreads();
   }
 
+  enableCodeCoverage = op.getBoolOption("code-coverage");
+  if (enableCodeCoverage) {
+    coverage::EnableLCov();
+  }
+
   AutoLibraryLoader loader;
   MultiStringRange dllPaths = op.getMultiStringOption("dll");
   while (!dllPaths.empty()) {
diff --git a/js/src/vm/CodeCoverage.cpp b/js/src/vm/CodeCoverage.cpp
index 15a9b66a6279..ce21f9591428 100644
--- a/js/src/vm/CodeCoverage.cpp
+++ b/js/src/vm/CodeCoverage.cpp
@@ -599,6 +599,21 @@ bool LCovRealm::writeRealmName(JS::Realm* realm) {
   return !outTN_.hadOutOfMemory();
 }
 
+bool gLCovIsEnabled = false;
+
+void InitLCov() {
+  const char* outDir = getenv("JS_CODE_COVERAGE_OUTPUT_DIR");
+  if (outDir && *outDir != 0) {
+    EnableLCov();
+  }
+}
+
+void EnableLCov() {
+  MOZ_ASSERT(!JSRuntime::hasLiveRuntimes(),
+             "EnableLCov must not be called after creating a runtime!");
+  gLCovIsEnabled = true;
+}
+
 LCovRuntime::LCovRuntime() : out_(), pid_(getpid()), isEmpty_(true) {}
 
 LCovRuntime::~LCovRuntime() {
diff --git a/js/src/vm/CodeCoverage.h b/js/src/vm/CodeCoverage.h
index 31b81d97e5bf..f95ac67fe1ff 100644
--- a/js/src/vm/CodeCoverage.h
+++ b/js/src/vm/CodeCoverage.h
@@ -125,15 +125,6 @@ class LCovRuntime {
   // all the scripts executed in the current JSRuntime.
   void init();
 
-  // Check if we should collect code coverage information.
-  bool isEnabled() const {
-    static bool isEnabled_ = ([]() {
-      const char* outDir = getenv("JS_CODE_COVERAGE_OUTPUT_DIR");
-      return outDir && *outDir != 0;
-    })();
-    return isEnabled_;
-  }
-
   // Write the aggregated result of the code coverage of a realm
   // into a file.
   void writeLCovResult(LCovRealm& realm);
@@ -166,6 +157,15 @@ class LCovRuntime {
   bool isEmpty_;
 };
 
+extern void InitLCov();
+
+extern void EnableLCov();
+
+inline bool IsLCovEnabled() {
+  extern bool gLCovIsEnabled;
+  return gLCovIsEnabled;
+}
+
 }  // namespace coverage
 }  // namespace js
 
diff --git a/js/src/vm/Initialization.cpp b/js/src/vm/Initialization.cpp
index ed7fbf3ba663..080dc34c5643 100644
--- a/js/src/vm/Initialization.cpp
+++ b/js/src/vm/Initialization.cpp
@@ -114,6 +114,8 @@ JS_PUBLIC_API const char* JS::detail::InitWithFailureDiagnostic(
 
   js::gc::InitMemorySubsystem();  // Ensure gc::SystemPageSize() works.
 
+  js::coverage::InitLCov();
+
   RETURN_IF_FAIL(js::jit::InitProcessExecutableMemory());
 
   RETURN_IF_FAIL(js::MemoryProtectionExceptionHandler::install());
diff --git a/js/src/vm/JSContext.h b/js/src/vm/JSContext.h
index d1628568f571..1bffa8740542 100644
--- a/js/src/vm/JSContext.h
+++ b/js/src/vm/JSContext.h
@@ -287,7 +287,6 @@ struct JSContext : public JS::RootingContext,
     return runtime_->jitSupportsUnalignedAccesses;
   }
   bool jitSupportsSimd() const { return runtime_->jitSupportsSimd; }
-  bool lcovEnabled() const { return runtime_->lcovOutput().isEnabled(); }
 
   /*
    * "Entering" a realm changes cx->realm (which changes cx->global). Note
diff --git a/js/src/vm/JSScript.cpp b/js/src/vm/JSScript.cpp
index 8ae803a1e22c..57e28b79054c 100644
--- a/js/src/vm/JSScript.cpp
+++ b/js/src/vm/JSScript.cpp
@@ -3361,7 +3361,7 @@ JSScript* JSScript::Create(JSContext* cx, const ReadOnlyCompileOptions& options,
   script->setFlag(MutableFlags::TrackRecordReplayProgress,
                   ShouldTrackRecordReplayProgress(script));
 
-  if (cx->runtime()->lcovOutput().isEnabled()) {
+  if (coverage::IsLCovEnabled()) {
     if (!script->initScriptName(cx)) {
       return nullptr;
     }
@@ -3714,8 +3714,8 @@ void JSScript::finalize(FreeOp* fop) {
 
   // Collect code coverage information for this script and all its inner
   // scripts, and store the aggregated information on the realm.
-  MOZ_ASSERT_IF(hasScriptName(), fop->runtime()->lcovOutput().isEnabled());
-  if (fop->runtime()->lcovOutput().isEnabled() && hasScriptName()) {
+  MOZ_ASSERT_IF(hasScriptName(), coverage::IsLCovEnabled());
+  if (coverage::IsLCovEnabled() && hasScriptName()) {
     realm()->lcovOutput.collectCodeCoverageInfo(realm(), this, getScriptName());
     destroyScriptName();
   }
diff --git a/js/src/vm/Realm.cpp b/js/src/vm/Realm.cpp
index 2b3ca1dae31e..f41679a6a4c3 100644
--- a/js/src/vm/Realm.cpp
+++ b/js/src/vm/Realm.cpp
@@ -62,9 +62,8 @@ Realm::~Realm() {
   MOZ_ASSERT(!hasBeenEnteredIgnoringJit());
 
   // Write the code coverage information in a file.
-  JSRuntime* rt = runtimeFromMainThread();
-  if (rt->lcovOutput().isEnabled()) {
-    rt->lcovOutput().writeLCovResult(lcovOutput);
+  if (coverage::IsLCovEnabled()) {
+    runtime_->lcovOutput().writeLCovResult(lcovOutput);
   }
 
   MOZ_ASSERT(runtime_->numRealms > 0);
@@ -826,9 +825,7 @@ bool Realm::collectCoverageForPGO() const {
 }
 
 bool Realm::collectCoverageForDebug() const {
-  return debuggerObservesCoverage() ||
-         runtimeFromAnyThread()->profilingScripts ||
-         runtimeFromAnyThread()->lcovOutput().isEnabled();
+  return debuggerObservesCoverage() || coverage::IsLCovEnabled();
 }
 
 void Realm::clearScriptCounts() {