diff --git a/src/parsers/atrules.ts b/src/parsers/atrules.ts
index 62e73cf5..fedb647f 100644
--- a/src/parsers/atrules.ts
+++ b/src/parsers/atrules.ts
@@ -122,7 +122,14 @@ export const parseKeyFrames = (css: Root): void => {
                 return;
             }
 
-            const rootFlipped = postcss.parse(atRuleFlippedString);
+            /* the source could be undefined in certain cases but not during the tests */
+            /* istanbul ignore next */
+            const rootFlipped = postcss.parse(
+                atRuleFlippedString,
+                {
+                    from: atRule.source?.input?.from
+                }
+            );
             const atRuleFlipped = rootFlipped.first as AtRule;
 
             const atRuleParams = atRule.params;
diff --git a/src/parsers/rules.ts b/src/parsers/rules.ts
index 06ae11a8..6bf7705d 100644
--- a/src/parsers/rules.ts
+++ b/src/parsers/rules.ts
@@ -51,7 +51,14 @@ export const parseRules = (
                 controlDirective.option
             ) {
                 const sourceDirectiveValue = getSourceDirectiveValue(controlDirectives);
-                const root = postcss.parse(controlDirective.option);
+                /* the source could be undefined in certain cases but not during the tests */
+                /* istanbul ignore next */
+                const root = postcss.parse(
+                    controlDirective.option,
+                    {
+                        from: container.source?.input?.from
+                    }
+                );
                 if (mode !== Mode.diff) {
                     root.walkRules((rule: Rule): void => {
                         addSelectorPrefixes(