diff --git a/babel.config.js b/babel.config.js
index 1746d9728970..1ec169604ab5 100644
--- a/babel.config.js
+++ b/babel.config.js
@@ -36,6 +36,7 @@ module.exports = function(api) {
     case "standalone":
       includeRegeneratorRuntime = true;
       unambiguousSources.push("packages/babel-runtime/regenerator");
+    // fall through
     case "rollup":
       convertESM = false;
       ignoreLib = false;
diff --git a/packages/babel-core/src/config/files/module-types.js b/packages/babel-core/src/config/files/module-types.js
index f90fb40b516d..2cffeb613d84 100644
--- a/packages/babel-core/src/config/files/module-types.js
+++ b/packages/babel-core/src/config/files/module-types.js
@@ -21,6 +21,7 @@ export default function* loadCjsOrMjsDefault(
       } catch (e) {
         if (e.code !== "ERR_REQUIRE_ESM") throw e;
       }
+    // fall through
     case "mjs":
       if (yield* isAsync()) {
         return yield* waitFor(loadMjsDefault(filepath));
diff --git a/packages/babel-parser/src/parser/expression.js b/packages/babel-parser/src/parser/expression.js
index 74f78c6047ac..0af61a473bd6 100644
--- a/packages/babel-parser/src/parser/expression.js
+++ b/packages/babel-parser/src/parser/expression.js
@@ -1058,7 +1058,7 @@ export default class ExpressionParser extends LValParser {
 
       case tt.at:
         this.parseDecorators();
-
+      // fall through
       case tt._class:
         node = this.startNode();
         this.takeDecorators(node);
@@ -1111,7 +1111,7 @@ export default class ExpressionParser extends LValParser {
           return this.finishNode(node, "PipelinePrimaryTopicReference");
         }
       }
-
+      // fall through
       default:
         throw this.unexpected();
     }
diff --git a/packages/babel-parser/src/plugins/flow.js b/packages/babel-parser/src/plugins/flow.js
index 29a8c8e69f24..58e78eaf6522 100644
--- a/packages/babel-parser/src/plugins/flow.js
+++ b/packages/babel-parser/src/plugins/flow.js
@@ -1441,7 +1441,7 @@ export default (superClass: Class<Parser>): Class<Parser> =>
             );
           }
 
-          this.unexpected();
+          throw this.unexpected();
         case tt.num:
           return this.parseLiteral(
             this.state.value,
diff --git a/packages/babel-parser/src/tokenizer/index.js b/packages/babel-parser/src/tokenizer/index.js
index 8558137f719f..63169b531117 100644
--- a/packages/babel-parser/src/tokenizer/index.js
+++ b/packages/babel-parser/src/tokenizer/index.js
@@ -332,7 +332,7 @@ export default class Tokenizer extends LocationParser {
           ) {
             ++this.state.pos;
           }
-
+        // fall through
         case charCodes.lineFeed:
         case charCodes.lineSeparator:
         case charCodes.paragraphSeparator:
@@ -736,7 +736,7 @@ export default class Tokenizer extends LocationParser {
         }
       }
       // Anything else beginning with a digit is an integer, octal
-      // number, or float.
+      // number, or float. (fall through)
       case charCodes.digit1:
       case charCodes.digit2:
       case charCodes.digit3:
@@ -1221,6 +1221,7 @@ export default class Tokenizer extends LocationParser {
             if (this.input.charCodeAt(this.state.pos) === charCodes.lineFeed) {
               ++this.state.pos;
             }
+          // fall through
           case charCodes.lineFeed:
             out += "\n";
             break;
@@ -1268,9 +1269,11 @@ export default class Tokenizer extends LocationParser {
         if (this.input.charCodeAt(this.state.pos) === charCodes.lineFeed) {
           ++this.state.pos;
         }
+      // fall through
       case charCodes.lineFeed:
         this.state.lineStart = this.state.pos;
         ++this.state.curLine;
+      // fall through
       case charCodes.lineSeparator:
       case charCodes.paragraphSeparator:
         return "";
@@ -1279,6 +1282,7 @@ export default class Tokenizer extends LocationParser {
         if (inTemplate) {
           return null;
         }
+      // fall through
       default:
         if (ch >= charCodes.digit0 && ch <= charCodes.digit7) {
           const codePos = this.state.pos - 1;
diff --git a/packages/babel-types/src/validators/isReferenced.js b/packages/babel-types/src/validators/isReferenced.js
index 847738fa4c43..9ae72f9423d2 100644
--- a/packages/babel-types/src/validators/isReferenced.js
+++ b/packages/babel-types/src/validators/isReferenced.js
@@ -54,16 +54,18 @@ export default function isReferenced(
       if (parent.params.includes(node)) {
         return false;
       }
-    // Fall-through to next case clause to check whether the node is the method's name.
+    // fall through
 
     // yes: { [NODE]: "" }
     // no: { NODE: "" }
     // depends: { NODE }
     // depends: { key: NODE }
+    // fall through
     case "ObjectProperty":
     // no: class { NODE = value; }
     // yes: class { [NODE] = value; }
     // yes: class { key = NODE; }
+    // fall through
     case "ClassProperty":
     case "ClassPrivateProperty":
       if (parent.key === node) {