diff --git a/tests/test-data.R b/tests/test-data.R
index 3d87a918..98116323 100644
--- a/tests/test-data.R
+++ b/tests/test-data.R
@@ -540,5 +540,36 @@ test_that("Compare two ProjectData Objects with commit.interactions", {
     commit.data[["hash"]][[5]] = 1
     proj.data.one$set.commits(commit.data)
 
-    expect_false(isTRUE(all.equal(proj.data.one$get.commit.interactions(), proj.data.two$get.commit.interactions())))
+    expect_false(isTRUE(all.equal(proj.data.one$get.commit.interactions(),
+                                  proj.data.two$get.commit.interactions())))
+
+    ## set commit list of one project data to empty and test that last
+    ## two rows of result data frame are empty
+    proj.data.two$set.commits(create.empty.commits.list())
+
+    ## create empty data frame of correct size
+    commit.interactions.data.expected = data.frame(matrix(nrow = 4, ncol = 8))
+    ## assure that the correct type is used
+    for(i in seq_len(8)) {
+        commit.interactions.data.expected[[i]] = as.character(commit.interactions.data.expected[[i]])
+    }
+    ## set everything except for authors as expected
+    colnames(commit.interactions.data.expected) = c("commit.hash", "base.hash", "func", "file",
+                                                    "base.func", "base.file", "base.author",
+                                                    "interacting.author")
+    commit.interactions.data.expected[["commit.hash"]] =
+                                                        c("0a1a5c523d835459c42f33e863623138555e2526",
+                                                        "418d1dc4929ad1df251d2aeb833dd45757b04a6f",
+                                                        "5a5ec9675e98187e1e92561e1888aa6f04faa338",
+                                                        "d01921773fae4bed8186b0aa411d6a2f7a6626e6")
+    commit.interactions.data.expected[["base.hash"]] =
+                                                      c("3a0ed78458b3976243db6829f63eba3eead26774",
+                                                        "0a1a5c523d835459c42f33e863623138555e2526",
+                                                        "72c8dd25d3dd6d18f46e2b26a5f5b1e2e8dc28d0",
+                                                        "0a1a5c523d835459c42f33e863623138555e2526")
+    commit.interactions.data.expected[["func"]] = c("test2.c", "test2.c", "test.c", "test2.c")
+    commit.interactions.data.expected[["file"]] = c("test2.c", "test2.c", "test.c", "test2.c")
+    commit.interactions.data.expected[["base.func"]] = c("test2.c", "test2.c", "test.c", "test2.c")
+    commit.interactions.data.expected[["base.file"]] = c("test2.c", "test2.c", "test.c", "test2.c")
+    expect_equal(proj.data.two$get.commit.interactions(), commit.interactions.data.expected)
 })
diff --git a/util-data.R b/util-data.R
index cdcf2f72..9ea12d8d 100644
--- a/util-data.R
+++ b/util-data.R
@@ -420,11 +420,11 @@ ProjectData = R6::R6Class("ProjectData",
 
             ## remove existing columns named 'base.author' and 'interaction.author'
             indices.to.remove = which("base.author" == colnames(private$commit.interactions))
-            if (length(indices.to.remove)>0) {
+            if (length(indices.to.remove) > 0) {
                 private$commit.interactions = private$commit.interactions[, -indices.to.remove]
             }
             indices.to.remove = which("interacting.author" == colnames(private$commit.interactions))
-            if (length(indices.to.remove)>0) {
+            if (length(indices.to.remove) > 0) {
                 private$commit.interactions = private$commit.interactions[, -indices.to.remove]
             }
 
@@ -435,17 +435,24 @@ ProjectData = R6::R6Class("ProjectData",
 
             ## merge commit interactions with commits and change colnames to avoid duplicates
             commit.interaction.data = merge(private$commit.interactions, commit.data.subset,
-                                            by.x = "base.hash", by.y = "hash")
+                                            by.x = "base.hash", by.y = "hash", all.x = TRUE)
 
             author.index = match("author.name", colnames(commit.interaction.data))
             colnames(commit.interaction.data)[[author.index]] = "base.author"
 
             commit.interaction.data = merge(commit.interaction.data, commit.data.subset,
-                                            by.x = "commit.hash", by.y = "hash")
+                                            by.x = "commit.hash", by.y = "hash", all.x = TRUE)
 
             author.index = match("author.name", colnames(commit.interaction.data))
             colnames(commit.interaction.data)[[author.index]] = "interacting.author"
 
+            ## warning if we have interactions without authors
+            if (anyNA(commit.interaction.data[["base.author"]]) ||
+                anyNA(commit.interaction.data[["interacting.author"]])) {
+                logging::logwarn("There are authors in the commit-interactions that are not in the commit data!
+                                  This results in the commit-interactions having empty entries.
+                                  To clean up these entries, call cleanup.commit.interactions.")
+            }
             private$commit.interactions = commit.interaction.data
 
         },