diff --git a/test/transform/resource/after-delombok/SingularCleanupForDelombok.java b/test/transform/resource/after-delombok/SingularCleanupForDelombok.java
new file mode 100644
index 00000000..69ae310d
--- /dev/null
+++ b/test/transform/resource/after-delombok/SingularCleanupForDelombok.java
@@ -0,0 +1,98 @@
+import java.util.Set;
+import lombok.NonNull;
+class Book {
+	@NonNull
+	private final String name;
+	@NonNull
+	private final Set<String> authors;
+	private final int numberOfAuthors;
+	public Book(String name, Set<String> authors) {
+		this(name, authors, authors.size());
+	}
+	@java.lang.SuppressWarnings("all")
+	public static class BookBuilder {
+		@java.lang.SuppressWarnings("all")
+		private String name;
+		@java.lang.SuppressWarnings("all")
+		private java.util.ArrayList<String> authors;
+		@java.lang.SuppressWarnings("all")
+		BookBuilder() {
+		}
+		/**
+		 * @return {@code this}.
+		 */
+		@java.lang.SuppressWarnings("all")
+		public Book.BookBuilder name(final String name) {
+			this.name = name;
+			return this;
+		}
+		@java.lang.SuppressWarnings("all")
+		public Book.BookBuilder author(final String author) {
+			if (this.authors == null) this.authors = new java.util.ArrayList<String>();
+			this.authors.add(author);
+			return this;
+		}
+		@java.lang.SuppressWarnings("all")
+		public Book.BookBuilder authors(final java.util.Collection<? extends String> authors) {
+			if (authors == null) {
+				throw new java.lang.NullPointerException("authors cannot be null");
+			}
+			if (this.authors == null) this.authors = new java.util.ArrayList<String>();
+			this.authors.addAll(authors);
+			return this;
+		}
+		@java.lang.SuppressWarnings("all")
+		public Book.BookBuilder clearAuthors() {
+			if (this.authors != null) this.authors.clear();
+			return this;
+		}
+		@java.lang.SuppressWarnings("all")
+		public Book build() {
+			java.util.Set<String> authors;
+			switch (this.authors == null ? 0 : this.authors.size()) {
+			case 0: 
+				authors = java.util.Collections.emptySet();
+				break;
+			case 1: 
+				authors = java.util.Collections.singleton(this.authors.get(0));
+				break;
+			default: 
+				authors = new java.util.LinkedHashSet<String>(this.authors.size() < 1073741824 ? 1 + this.authors.size() + (this.authors.size() - 3) / 3 : java.lang.Integer.MAX_VALUE);
+				authors.addAll(this.authors);
+				authors = java.util.Collections.unmodifiableSet(authors);
+			}
+			return new Book(this.name, authors);
+		}
+		@java.lang.Override
+		@java.lang.SuppressWarnings("all")
+		public java.lang.String toString() {
+			return "Book.BookBuilder(name=" + this.name + ", authors=" + this.authors + ")";
+		}
+	}
+	@java.lang.SuppressWarnings("all")
+	public static Book.BookBuilder builder() {
+		return new Book.BookBuilder();
+	}
+	@java.lang.SuppressWarnings("all")
+	Book(@NonNull final String name, @NonNull final Set<String> authors, final int numberOfAuthors) {
+		if (name == null) {
+			throw new java.lang.NullPointerException("name is marked non-null but is null");
+		}
+		if (authors == null) {
+			throw new java.lang.NullPointerException("authors is marked non-null but is null");
+		}
+		this.name = name;
+		this.authors = authors;
+		this.numberOfAuthors = numberOfAuthors;
+	}
+	@NonNull
+	@java.lang.SuppressWarnings("all")
+	public String name() {
+		return this.name;
+	}
+	@NonNull
+	@java.lang.SuppressWarnings("all")
+	public Set<String> authors() {
+		return this.authors;
+	}
+}
\ No newline at end of file
diff --git a/test/transform/resource/after-ecj/SingularCleanupForDelombok.java b/test/transform/resource/after-ecj/SingularCleanupForDelombok.java
new file mode 100644
index 00000000..4036105d
--- /dev/null
+++ b/test/transform/resource/after-ecj/SingularCleanupForDelombok.java
@@ -0,0 +1 @@
+// ignore: This tests specifically that delombok removes something; it does not apply to ecj
diff --git a/test/transform/resource/before/SingularCleanupForDelombok.java b/test/transform/resource/before/SingularCleanupForDelombok.java
new file mode 100644
index 00000000..49ed8b1e
--- /dev/null
+++ b/test/transform/resource/before/SingularCleanupForDelombok.java
@@ -0,0 +1,23 @@
+// issue #1377: @Singular is not removed by delombok.
+
+import java.util.Set;
+
+import lombok.AccessLevel;
+import lombok.AllArgsConstructor;
+import lombok.Builder;
+import lombok.Getter;
+import lombok.NonNull;
+import lombok.Singular;
+
+import lombok.experimental.Accessors;
+import lombok.experimental.FieldDefaults;
+
+@Accessors(fluent = true) @AllArgsConstructor(access = AccessLevel.PACKAGE) @FieldDefaults(makeFinal = true, level = AccessLevel.PRIVATE) class Book {
+	@Getter @NonNull String name;
+	@Getter @Singular @NonNull Set<String> authors;
+	int numberOfAuthors;
+	
+	@Builder public Book(String name, @Singular Set<String> authors) {
+		this(name, authors, authors.size());
+	}
+}
\ No newline at end of file