diff --git a/CHANGELOG.md b/CHANGELOG.md
index 3780bee035..2df3c2f8bd 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -4,6 +4,7 @@ Changes
 ## Unreleased
 
 - LsiModel: Only log top words that actually exist in the dictionary (PR [#3091](https://github.com/RaRe-Technologies/gensim/pull/3091), [@kmurphy4](https://github.com/kmurphy4))
+- Materialize and copy the corpus passed to SoftCosineSimilarity (PR [#3128](https://github.com/RaRe-Technologies/gensim/pull/3128), [@Witiko](https://github.com/Witiko))
 - [#3115](https://github.com/RaRe-Technologies/gensim/pull/3115): Make LSI dispatcher CLI param for number of jobs optional, by [@robguinness](https://github.com/robguinness))
 
 ### Documentation
diff --git a/gensim/similarities/docsim.py b/gensim/similarities/docsim.py
index 4dd0528f50..d9d1ca31d9 100755
--- a/gensim/similarities/docsim.py
+++ b/gensim/similarities/docsim.py
@@ -937,7 +937,7 @@ def __init__(self, corpus, similarity_matrix, num_best=None, chunksize=256, norm
         """
         self.similarity_matrix = similarity_matrix
 
-        self.corpus = corpus
+        self.corpus = list(corpus)
         self.num_best = num_best
         self.chunksize = chunksize
         self.normalized = normalized