diff --git a/README.md b/README.md
index 97761ab..93713aa 100644
--- a/README.md
+++ b/README.md
@@ -62,7 +62,7 @@ The file formats can optionally be provided as the 3rd and 4th parameter for the
 
 To convert from SPDX 2 to SPDX 3.0.1:
 
-* use the file extension `.jsonld.json` or `.jsonld`;
+* use the file extension `.spdx3.json` or `.jsonld.json` or `.jsonld`;
 * or add the options for the from and to file types:
 
     java -jar tools-java-2.0.5-jar-with-dependencies.jar Convert hello.spdx hello.spdx.json TAG JSONLD
diff --git a/src/main/java/org/spdx/tools/SpdxToolsHelper.java b/src/main/java/org/spdx/tools/SpdxToolsHelper.java
index dfa9402..59ab84e 100644
--- a/src/main/java/org/spdx/tools/SpdxToolsHelper.java
+++ b/src/main/java/org/spdx/tools/SpdxToolsHelper.java
@@ -70,6 +70,7 @@ public enum SerFileType {
 	static Map<String, SerFileType> EXT_TO_FILETYPE;
 	static {
 		HashMap<String, SerFileType> temp = new HashMap<>();
+		temp.put("spdx3.json", SerFileType.JSONLD);
 		temp.put("jsonld.json", SerFileType.JSONLD);
 		temp.put("jsonld", SerFileType.JSONLD);
 		temp.put("json", SerFileType.JSON);
@@ -159,10 +160,14 @@ public static SerFileType fileToFileType(File file)
 			if (fileName.endsWith("rdf.ttl")) {
 				ext = "rdf.ttl";
 			}
-		}if ("json".equals(ext)) {
+		}
+		if ("json".equals(ext)) {
 			if (fileName.endsWith("jsonld.json")) {
 				ext = "jsonld.json";
 			}
+			if (fileName.endsWith("spdx3.json")) {
+				ext = "spdx3.json";
+			}
 		}
 		SerFileType retval = EXT_TO_FILETYPE.get(ext);
 		if (SerFileType.JSON.equals(retval)) {