diff --git a/src/main/java/com/structurizr/dsl/IdentifiersRegister.java b/src/main/java/com/structurizr/dsl/IdentifiersRegister.java
index bef26ce..ecbef0c 100644
--- a/src/main/java/com/structurizr/dsl/IdentifiersRegister.java
+++ b/src/main/java/com/structurizr/dsl/IdentifiersRegister.java
@@ -16,7 +16,7 @@
  */
 public class IdentifiersRegister {
 
-    private static final Pattern IDENTIFIER_PATTERN = Pattern.compile("\\w+");
+    private static final Pattern IDENTIFIER_PATTERN = Pattern.compile("\\w[a-zA-Z0-9_-]*");
 
     private IdentifierScope identifierScope = IdentifierScope.Flat;
 
@@ -180,8 +180,12 @@ public String findIdentifier(Relationship relationship) {
     }
 
     void validateIdentifierName(String identifier) {
+        if (identifier.startsWith("-")) {
+            throw new RuntimeException("Identifiers cannot start with a - character");
+        }
+
         if (!IDENTIFIER_PATTERN.matcher(identifier).matches()) {
-            throw new RuntimeException("Identifiers can only contain the following characters: a-zA-Z_0-9");
+            throw new RuntimeException("Identifiers can only contain the following characters: a-zA-Z0-9_-");
         }
     }
 
diff --git a/src/test/java/com/structurizr/dsl/IdentifierRegisterTests.java b/src/test/java/com/structurizr/dsl/IdentifierRegisterTests.java
index 39188dc..15936e9 100644
--- a/src/test/java/com/structurizr/dsl/IdentifierRegisterTests.java
+++ b/src/test/java/com/structurizr/dsl/IdentifierRegisterTests.java
@@ -8,7 +8,33 @@
 
 class IdentifierRegisterTests extends AbstractTests {
 
-    private IdentifiersRegister register = new IdentifiersRegister();
+    private final IdentifiersRegister register = new IdentifiersRegister();
+
+    @Test
+    void test_validateIdentifierName() {
+        new IdentifiersRegister().validateIdentifierName("a");
+        new IdentifiersRegister().validateIdentifierName("abc");
+        new IdentifiersRegister().validateIdentifierName("ABC");
+        new IdentifiersRegister().validateIdentifierName("softwaresystem");
+        new IdentifiersRegister().validateIdentifierName("SoftwareSystem");
+        new IdentifiersRegister().validateIdentifierName("123456");
+        new IdentifiersRegister().validateIdentifierName("_softwareSystem");
+        new IdentifiersRegister().validateIdentifierName("SoftwareSystem-1");
+
+        try {
+            new IdentifiersRegister().validateIdentifierName("-softwareSystem");
+            fail();
+        } catch (Exception e) {
+            assertEquals("Identifiers cannot start with a - character", e.getMessage());
+        }
+
+        try {
+            new IdentifiersRegister().validateIdentifierName("SoftwareSystém");
+            fail();
+        } catch (Exception e) {
+            assertEquals("Identifiers can only contain the following characters: a-zA-Z0-9_-", e.getMessage());
+        }
+    }
 
     @Test
     void test_register_ThrowsAnException_WhenTheElementHasAlreadyBeenRegisteredWithADifferentIdentifier() {