diff --git a/packages/block-library/src/pattern/edit.js b/packages/block-library/src/pattern/edit.js
index e8068faf5013d9..b52c50ec564c54 100644
--- a/packages/block-library/src/pattern/edit.js
+++ b/packages/block-library/src/pattern/edit.js
@@ -37,13 +37,7 @@ const PatternEdit = ( { attributes, clientId } ) => {
 			)
 		) {
 			block.innerBlocks = block.innerBlocks.map( ( innerBlock ) => {
-				if (
-					innerBlock.name === 'core/template-part' &&
-					innerBlock.attributes.theme === undefined
-				) {
-					innerBlock.attributes.theme = currentThemeStylesheet;
-				}
-				return innerBlock;
+				return injectThemeAttributeInBlockTemplateContent( innerBlock );
 			} );
 		}
 
diff --git a/packages/edit-site/src/components/start-template-options/index.js b/packages/edit-site/src/components/start-template-options/index.js
index fe4179a338504b..4fc113bc46912f 100644
--- a/packages/edit-site/src/components/start-template-options/index.js
+++ b/packages/edit-site/src/components/start-template-options/index.js
@@ -63,13 +63,7 @@ function useStartPatterns( fallbackContent ) {
 			)
 		) {
 			block.innerBlocks = block.innerBlocks.map( ( innerBlock ) => {
-				if (
-					innerBlock.name === 'core/template-part' &&
-					innerBlock.attributes.theme === undefined
-				) {
-					innerBlock.attributes.theme = currentThemeStylesheet;
-				}
-				return innerBlock;
+				return injectThemeAttributeInBlockTemplateContent( innerBlock );
 			} );
 		}