diff --git a/lib/optimize/ModuleConcatenationPlugin.js b/lib/optimize/ModuleConcatenationPlugin.js
index 94ce1a965..12d6f662b 100644
--- a/lib/optimize/ModuleConcatenationPlugin.js
+++ b/lib/optimize/ModuleConcatenationPlugin.js
@@ -315,12 +315,13 @@ class ModuleConcatenationPlugin {
 								// _tryToAdd modifies the config even if it fails
 								// so make sure to only accept changes when it succeed
 								const backup = currentConfiguration.snapshot();
+								const impCandiates = new Set();
 								const problem = this._tryToAdd(
 									compilation,
 									currentConfiguration,
 									imp,
 									possibleInners,
-									candidates,
+									impCandiates,
 									failureCache
 								);
 								if (problem) {
@@ -329,6 +330,10 @@ class ModuleConcatenationPlugin {
 
 									// roll back
 									currentConfiguration.rollback(backup);
+								} else {
+									for (const c of impCandiates) {
+										candidates.add(c);
+									}
 								}
 							}
 							if (!currentConfiguration.isEmpty()) {