diff --git a/common/changes/@microsoft/rush/fix-edge-case-rush-does-not-update-lockfile_2024-08-30-06-44.json b/common/changes/@microsoft/rush/fix-edge-case-rush-does-not-update-lockfile_2024-08-30-06-44.json
new file mode 100644
index 00000000000..de0df7be96b
--- /dev/null
+++ b/common/changes/@microsoft/rush/fix-edge-case-rush-does-not-update-lockfile_2024-08-30-06-44.json
@@ -0,0 +1,10 @@
+{
+  "changes": [
+    {
+      "packageName": "@microsoft/rush",
+      "comment": "Fix an issue where moving dependencies from `dependencies` to `devDependencies` in a project's `package.json` did not trigger an lockfile update.",
+      "type": "none"
+    }
+  ],
+  "packageName": "@microsoft/rush"
+}
\ No newline at end of file
diff --git a/libraries/rush-lib/src/logic/pnpm/PnpmShrinkwrapFile.ts b/libraries/rush-lib/src/logic/pnpm/PnpmShrinkwrapFile.ts
index 52fbd234f81..e107a02f664 100644
--- a/libraries/rush-lib/src/logic/pnpm/PnpmShrinkwrapFile.ts
+++ b/libraries/rush-lib/src/logic/pnpm/PnpmShrinkwrapFile.ts
@@ -1002,9 +1002,9 @@ export class PnpmShrinkwrapFile extends BaseShrinkwrapFile {
             }
             // If fall through, there is a chance the package declares an inconsistent version, ignore it.
             isDevDepFallThrough = true;
+            break;
           }
 
-          // eslint-disable-next-line no-fallthrough
           case DependencyType.Regular:
             specifierFromLockfile = importer.dependencies?.[name];
             importerDependencies.delete(name);
diff --git a/libraries/rush-lib/src/logic/pnpm/test/PnpmShrinkwrapFile.test.ts b/libraries/rush-lib/src/logic/pnpm/test/PnpmShrinkwrapFile.test.ts
index b433514c8ce..37d22a6fa93 100644
--- a/libraries/rush-lib/src/logic/pnpm/test/PnpmShrinkwrapFile.test.ts
+++ b/libraries/rush-lib/src/logic/pnpm/test/PnpmShrinkwrapFile.test.ts
@@ -218,7 +218,7 @@ describe(PnpmShrinkwrapFile.name, () => {
             project,
             project.rushConfiguration.defaultSubspace
           )
-        ).resolves.toBe(false);
+        ).resolves.toBe(true);
       });
     });
   });