--- a/js/src/frontend/BinTokenReaderBase.h
+++ b/js/src/frontend/BinTokenReaderBase.h
@@ -104,19 +104,24 @@ class MOZ_STACK_CLASS BinTokenReaderBase
     MOZ_MUST_USE bool matchConst(const char (&value)[N], bool expectNul) {
         MOZ_ASSERT(N > 0);
         MOZ_ASSERT(value[N - 1] == 0);
         MOZ_ASSERT(!cx_->isExceptionPending());
 
         if (current_ + N - 1 > stop_)
             return false;
 
+#ifndef FUZZING
         // Perform lookup, without side-effects.
+        // For fuzzing, we disable this check to avoid spending unnecessary
+        // time on getting the constants right. Instead, the constant fields
+        // may contain any data for such builds.
         if (!std::equal(current_, current_ + N + (expectNul ? 0 : -1)/*implicit NUL*/, value))
             return false;
+#endif
 
         // Looks like we have a match. Now perform side-effects
         current_ += N + (expectNul ? 0 : -1);
         updateLatestKnownGood();
         return true;
     }
 
     void updateLatestKnownGood();
@@ -143,9 +148,9 @@ class MOZ_STACK_CLASS BinTokenReaderBase
     BinTokenReaderBase(const BinTokenReaderBase&) = delete;
     BinTokenReaderBase(BinTokenReaderBase&&) = delete;
     BinTokenReaderBase& operator=(BinTokenReaderBase&) = delete;
 };
 
 } // namespace frontend
 } // namespace js
 
-#endif // frontend_BinTokenReaderBase_h
\ No newline at end of file
+#endif // frontend_BinTokenReaderBase_h

--- a/js/src/fuzz-tests/testBinASTReader.cpp
+++ b/js/src/fuzz-tests/testBinASTReader.cpp
@@ -51,17 +51,17 @@ testBinASTReaderFuzz(const uint8_t* buf,
     }
 
     js::frontend::UsedNameTracker binUsedNames(gCx);
     if (!binUsedNames.init()) {
         ReportOutOfMemory(gCx);
         return 0;
     }
 
-    js::frontend::BinASTParser<js::frontend::BinTokenReaderTester> reader(gCx, gCx->tempLifoAlloc(), binUsedNames, options);
+    js::frontend::BinASTParser<js::frontend::BinTokenReaderMultipart> reader(gCx, gCx->tempLifoAlloc(), binUsedNames, options);
 
     // Will be deallocated once `reader` goes out of scope.
     auto binParsed = reader.parse(binSource);
     RootedValue binExn(gCx);
     if (binParsed.isErr()) {
         js::GetAndClearException(gCx, &binExn);
         return 0;
     }

--- a/js/src/moz.build
+++ b/js/src/moz.build
@@ -714,19 +714,21 @@ if CONFIG['JS_BUILD_BINAST']:
         'frontend/BinSource.cpp',
         'frontend/BinToken.cpp',
         'frontend/BinTokenReaderBase.cpp',
         'frontend/BinTokenReaderMultipart.cpp',
     ]
 
     # Instrument BinAST files for fuzzing as we have a fuzzing target for BinAST.
     if CONFIG['FUZZING_INTERFACES'] and CONFIG['LIBFUZZER']:
+        SOURCES['frontend/BinSource-auto.cpp'].flags += libfuzzer_flags_cmp
         SOURCES['frontend/BinSource.cpp'].flags += libfuzzer_flags_cmp
         SOURCES['frontend/BinToken.cpp'].flags += libfuzzer_flags_cmp
-        SOURCES['frontend/BinTokenReaderTester.cpp'].flags += libfuzzer_flags_cmp
+        SOURCES['frontend/BinTokenReaderBase.cpp'].flags += libfuzzer_flags_cmp
+        SOURCES['frontend/BinTokenReaderMultipart.cpp'].flags += libfuzzer_flags_cmp
 
 # Wasm code should use WASM_HUGE_MEMORY instead of JS_CODEGEN_X64
 # so that it is easy to use the huge-mapping optimization for other
 # 64-bit platforms in the future.
 
 if CONFIG['JS_CODEGEN_X64'] or CONFIG['JS_CODEGEN_ARM64']:
     DEFINES['WASM_HUGE_MEMORY'] = True