diff --git a/packages/localize/src/tools/src/source_file_utils.ts b/packages/localize/src/tools/src/source_file_utils.ts
index e0814955e8..55cd10c5fa 100644
--- a/packages/localize/src/tools/src/source_file_utils.ts
+++ b/packages/localize/src/tools/src/source_file_utils.ts
@@ -89,7 +89,7 @@ export function unwrapMessagePartsFromLocalizeCall(
   // If there is no call to `__makeTemplateObject(...)`, then `raw` must be the same as `cooked`.
   let raw = cooked;
 
-  // Check for cached call of the form `x || x = __makeTemplateObject(...)`
+  // Check for a memoized form: `x || x = ...`
   if (cooked.isLogicalExpression() && cooked.node.operator === '||' &&
       cooked.get('left').isIdentifier()) {
     const right = cooked.get('right');
@@ -105,15 +105,22 @@ export function unwrapMessagePartsFromLocalizeCall(
         // This is a minified sequence expression, where the first two expressions in the sequence
         // are assignments of the cooked and raw arrays respectively.
         const [first, second] = expressions;
-        if (first.isAssignmentExpression() && second.isAssignmentExpression()) {
+        if (first.isAssignmentExpression()) {
           cooked = first.get('right');
           if (!cooked.isExpression()) {
             throw new BabelParseError(
                 first.node, 'Unexpected cooked value, expected an expression.');
           }
-          raw = second.get('right');
-          if (!raw.isExpression()) {
-            throw new BabelParseError(second.node, 'Unexpected raw value, expected an expression.');
+          if (second.isAssignmentExpression()) {
+            raw = second.get('right');
+            if (!raw.isExpression()) {
+              throw new BabelParseError(
+                  second.node, 'Unexpected raw value, expected an expression.');
+            }
+          } else {
+            // If the second expression is not an assignment then it is probably code to take a copy
+            // of the cooked array. For example: `raw || (raw=cooked.slice(0))`.
+            raw = cooked;
           }
         }
       }
diff --git a/packages/localize/src/tools/test/source_file_utils_spec.ts b/packages/localize/src/tools/test/source_file_utils_spec.ts
index 1f8421fcd7..249c4beef8 100644
--- a/packages/localize/src/tools/test/source_file_utils_spec.ts
+++ b/packages/localize/src/tools/test/source_file_utils_spec.ts
@@ -132,6 +132,104 @@ runInEachFileSystem(() => {
            ]);
          });
 
+      it('should return an array of string literals and locations from a (Babel helper) downleveled tagged template',
+         () => {
+           let localizeCall = getLocalizeCall(
+               `$localize(babelHelpers.taggedTemplateLiteral(['a', 'b\\t', 'c'], ['a', 'b\\\\t', 'c']), 1, 2)`);
+           const [parts, locations] = unwrapMessagePartsFromLocalizeCall(localizeCall, fs);
+           expect(parts).toEqual(['a', 'b\t', 'c']);
+           expect(parts.raw).toEqual(['a', 'b\\t', 'c']);
+           expect(locations).toEqual([
+             {
+               start: {line: 0, column: 65},
+               end: {line: 0, column: 68},
+               file: absoluteFrom('/test/file.js'),
+               text: `'a'`,
+             },
+             {
+               start: {line: 0, column: 70},
+               end: {line: 0, column: 76},
+               file: absoluteFrom('/test/file.js'),
+               text: `'b\\\\t'`,
+             },
+             {
+               start: {line: 0, column: 78},
+               end: {line: 0, column: 81},
+               file: absoluteFrom('/test/file.js'),
+               text: `'c'`,
+             },
+           ]);
+         });
+
+      it('should return an array of string literals and locations from a memoized downleveled tagged template',
+         () => {
+           let localizeCall = getLocalizeCall(`
+                var _templateObject;
+                $localize(_templateObject || (_templateObject = __makeTemplateObject(['a', 'b\\t', 'c'], ['a', 'b\\\\t', 'c'])), 1, 2)`);
+           const [parts, locations] = unwrapMessagePartsFromLocalizeCall(localizeCall, fs);
+           expect(parts).toEqual(['a', 'b\t', 'c']);
+           expect(parts.raw).toEqual(['a', 'b\\t', 'c']);
+           expect(locations).toEqual([
+             {
+               start: {line: 2, column: 105},
+               end: {line: 2, column: 108},
+               file: absoluteFrom('/test/file.js'),
+               text: `'a'`,
+             },
+             {
+               start: {line: 2, column: 110},
+               end: {line: 2, column: 116},
+               file: absoluteFrom('/test/file.js'),
+               text: `'b\\\\t'`,
+             },
+             {
+               start: {line: 2, column: 118},
+               end: {line: 2, column: 121},
+               file: absoluteFrom('/test/file.js'),
+               text: `'c'`,
+             },
+           ]);
+         });
+
+      it('should return an array of string literals and locations from a memoized (inlined Babel helper) downleveled tagged template',
+         () => {
+           let localizeCall = getLocalizeCall(`
+              var e,t,n;
+              $localize(e ||
+                (
+                  t=["a","b\t","c"],
+                  n || (n=t.slice(0)),
+                  e = Object.freeze(
+                    Object.defineProperties(t, { raw: { value: Object.freeze(n) } })
+                  )
+                ),
+                1,2
+              )`);
+           const [parts, locations] = unwrapMessagePartsFromLocalizeCall(localizeCall, fs);
+           expect(parts).toEqual(['a', 'b\t', 'c']);
+           expect(parts.raw).toEqual(['a', 'b\t', 'c']);
+           expect(locations).toEqual([
+             {
+               start: {line: 4, column: 21},
+               end: {line: 4, column: 24},
+               file: absoluteFrom('/test/file.js'),
+               text: `"a"`,
+             },
+             {
+               start: {line: 4, column: 25},
+               end: {line: 4, column: 29},
+               file: absoluteFrom('/test/file.js'),
+               text: `"b\t"`,
+             },
+             {
+               start: {line: 4, column: 30},
+               end: {line: 4, column: 33},
+               file: absoluteFrom('/test/file.js'),
+               text: `"c"`,
+             },
+           ]);
+         });
+
       it('should return an array of string literals and locations from a lazy load template helper',
          () => {
            let localizeCall = getLocalizeCall(`