diff --git a/cmd/eval-dev-quality/cmd/evaluate.go b/cmd/eval-dev-quality/cmd/evaluate.go
index c0d8c5ad..b8608a02 100644
--- a/cmd/eval-dev-quality/cmd/evaluate.go
+++ b/cmd/eval-dev-quality/cmd/evaluate.go
@@ -144,6 +144,15 @@ func (command *Evaluate) Initialize(args []string) (cleanup func()) {
 		}
 	}
 
+	// Ensure the "testdata" path exists and make it absolute.
+	if err := osutil.DirExists(command.TestdataPath); err != nil {
+		command.logger.Panicf("ERROR: testdata path %q cannot be accessed: %s", command.TestdataPath, err)
+	}
+	command.TestdataPath, err = filepath.Abs(command.TestdataPath)
+	if err != nil {
+		command.logger.Panicf("ERROR: could not resolve testdata path %q to an absolute path: %s", command.TestdataPath, err)
+	}
+
 	// Register custom OpenAI API providers and models.
 	{
 		customProviders := map[string]*openaiapi.Provider{}
@@ -205,25 +214,45 @@ func (command *Evaluate) Initialize(args []string) (cleanup func()) {
 	{
 		commandRepositories := map[string]bool{}
 		commandRepositoriesLanguages := map[string]bool{}
-		for _, r := range command.Repositories {
-			languageIDOfRepository := strings.SplitN(r, string(os.PathSeparator), 2)[0]
-			commandRepositoriesLanguages[languageIDOfRepository] = true
-
-			if _, ok := languagesSelected[languageIDOfRepository]; ok {
-				commandRepositories[r] = true
-			} else {
-				command.logger.Printf("Excluded repository %s because its language %q is not enabled for this evaluation", r, languageIDOfRepository)
+		if len(command.Repositories) == 0 {
+			for _, language := range command.Languages {
+				commandRepositoriesLanguages[language] = true
+				commandRepositories[filepath.Join(language, evaluate.RepositoryPlainName)] = true
+
+				languagePath := filepath.Join(command.TestdataPath, language)
+				languageRepositories, err := os.ReadDir(languagePath)
+				if err != nil {
+					command.logger.Panicf("ERROR: language path %q cannot be accessed: %s", languagePath, err)
+				}
+
+				for _, repository := range languageRepositories {
+					if !repository.IsDir() {
+						continue
+					}
+					commandRepositories[filepath.Join(language, repository.Name())] = true
+				}
 			}
-		}
-		for languageID := range languagesSelected {
-			if len(command.Repositories) == 0 || commandRepositoriesLanguages[languageID] {
-				commandRepositories[filepath.Join(languageID, evaluate.RepositoryPlainName)] = true
-			} else {
-				command.Languages = slices.DeleteFunc(command.Languages, func(l string) bool {
-					return l == languageID
-				})
-				delete(languagesSelected, languageID)
-				command.logger.Printf("Excluded language %q because it is not part of the selected repositories", languageID)
+		} else {
+			for _, r := range command.Repositories {
+				languageIDOfRepository := strings.SplitN(r, string(os.PathSeparator), 2)[0]
+				commandRepositoriesLanguages[languageIDOfRepository] = true
+
+				if _, ok := languagesSelected[languageIDOfRepository]; ok {
+					commandRepositories[r] = true
+				} else {
+					command.logger.Printf("Excluded repository %s because its language %q is not enabled for this evaluation", r, languageIDOfRepository)
+				}
+			}
+			for languageID := range languagesSelected {
+				if commandRepositoriesLanguages[languageID] {
+					commandRepositories[filepath.Join(languageID, evaluate.RepositoryPlainName)] = true
+				} else {
+					command.Languages = slices.DeleteFunc(command.Languages, func(l string) bool {
+						return l == languageID
+					})
+					delete(languagesSelected, languageID)
+					command.logger.Printf("Excluded language %q because it is not part of the selected repositories", languageID)
+				}
 			}
 		}
 		command.Repositories = maps.Keys(commandRepositories)
@@ -303,15 +332,6 @@ func (command *Evaluate) Initialize(args []string) (cleanup func()) {
 		}
 	}
 
-	// Ensure the "testdata" path exists and make it absolute.
-	if err := osutil.DirExists(command.TestdataPath); err != nil {
-		command.logger.Panicf("ERROR: testdata path %q cannot be accessed: %s", command.TestdataPath, err)
-	}
-	command.TestdataPath, err = filepath.Abs(command.TestdataPath)
-	if err != nil {
-		command.logger.Panicf("ERROR: could not resolve testdata path %q to an absolute path: %s", command.TestdataPath, err)
-	}
-
 	return nil
 }
 
diff --git a/cmd/eval-dev-quality/cmd/evaluate_test.go b/cmd/eval-dev-quality/cmd/evaluate_test.go
index ab8fa23b..12dda265 100644
--- a/cmd/eval-dev-quality/cmd/evaluate_test.go
+++ b/cmd/eval-dev-quality/cmd/evaluate_test.go
@@ -892,4 +892,25 @@ func TestEvaluateInitialize(t *testing.T) {
 			}, command.Languages)
 		},
 	})
+	validate(t, &testCase{
+		Name: "Selecting no repository defaults to all",
+
+		Command: makeValidCommand(func(command *Evaluate) {
+			command.Repositories = []string{}
+		}),
+
+		ValidateCommand: func(t *testing.T, command *Evaluate) {
+			// Check if all Go repositories are indeed selected.
+			directories, err := os.ReadDir(filepath.Join("..", "..", "..", "testdata", "golang"))
+			require.NoError(t, err)
+			relativeRepositoryPath := make([]string, len(directories))
+			for i, directory := range directories {
+				relativeRepositoryPath[i] = filepath.Join("golang", directory.Name())
+			}
+
+			for _, golangRepository := range relativeRepositoryPath {
+				assert.Contains(t, command.Repositories, golangRepository)
+			}
+		},
+	})
 }