diff --git a/src/main/java/io/vertx/json/schema/impl/Format.java b/src/main/java/io/vertx/json/schema/impl/Format.java
index 179a3782..7e1cb1e4 100644
--- a/src/main/java/io/vertx/json/schema/impl/Format.java
+++ b/src/main/java/io/vertx/json/schema/impl/Format.java
@@ -182,17 +182,19 @@ private static boolean testUri(String value) {
     return NOT_URI_FRAGMENT.matcher(value).find() && URI_PATTERN.matcher(value).find();
   }
 
-  private static final Pattern DURATION_A = Pattern.compile("^-?P\\d+([.,]\\d+)?W$");
-  private static final Pattern DURATIION_B = Pattern.compile("^-?P[\\dYMDTHS]*(\\d[.,]\\d+)?[YMDHS]$");
-  private static final Pattern DURATIION_C = Pattern.compile("^-?P([.,\\d]+Y)?([.,\\d]+M)?([.,\\d]+D)?(T([.,\\d]+H)?([.,\\d]+M)?([.,\\d]+S)?)?$");
-  // Matches to true if a duration string is not a zero duration with a minus sign in front.
-  private static final Pattern DURATION_D = Pattern.compile("^(-.*[1-9].*|[^-].*)$");
+
+  private static final Pattern DURATION_A = Pattern.compile("^P\\d+([.,]\\d+)?W$");
+  private static final Pattern DURATIION_B = Pattern.compile("^P[\\dYMDTHS]*(\\d[.,]\\d+)?[YMDHS]$");
+  private static final Pattern DURATIION_C = Pattern.compile("^P([.,\\d]+Y)?([.,\\d]+M)?([.,\\d]+D)?(T([.,\\d]+H)?([.,\\d]+M)?([.,\\d]+S)?)?$");
+  private static final Pattern DURATION_D = Pattern.compile("^-?P(-?\\d+(\\.\\d+)?Y)?(-?\\d+(\\.\\d+)?M)?(-?\\d+(\\.\\d+)?W)?(-?\\d+(\\.\\d+)?D)?(T(-?\\d+(\\.\\d+)?H)?(-?\\d+(\\.\\d+)?M)?(-?\\d+(\\.\\d+)?S)?)?$");
 
   private static boolean testDuration(String value) {
     return value.length() > 1 &&
       value.length() < 80 &&
-      (DURATION_A.matcher(value).find() || (DURATIION_B.matcher(value).find() && DURATIION_C.matcher(value).find())) &&
-      (DURATION_D.matcher(value).find());
+      (DURATION_A.matcher(value).find() ||
+        (DURATIION_B.matcher(value).find() &&
+          DURATIION_C.matcher(value).find())) ||
+      DURATION_D.matcher(value).find();
   }
 
   private static final Pattern FASTDATETIME = Pattern.compile("^\\d\\d\\d\\d-[0-1]\\d-[0-3]\\d[t\\s](?:[0-2]\\d:[0-5]\\d:[0-5]\\d|23:59:60)(?:\\.\\d+)?(?:z|[+-]\\d\\d(?::?\\d\\d)?)$", Pattern.CASE_INSENSITIVE);
diff --git a/src/test/java/io/vertx/json/schema/ValidationTest.java b/src/test/java/io/vertx/json/schema/ValidationTest.java
index f2aead54..5da22f1c 100644
--- a/src/test/java/io/vertx/json/schema/ValidationTest.java
+++ b/src/test/java/io/vertx/json/schema/ValidationTest.java
@@ -9,6 +9,8 @@
 import static org.assertj.core.api.Assertions.assertThat;
 import static org.assertj.core.api.Assertions.fail;
 
+import java.util.function.Consumer;
+
 @ExtendWith(VertxExtension.class)
 class ValidationTest {
 
@@ -226,7 +228,7 @@ public void testIssue49b() throws JsonSchemaValidationException {
   }
 
   @Test
-  void testNegativeDurationValidation() throws JsonSchemaValidationException {
+  void testDurationValidation() {
 
     SchemaRepository repository = SchemaRepository.create(new JsonSchemaOptions().setDraft(Draft.DRAFT201909).setBaseUri("app://"));
 
@@ -246,19 +248,43 @@ void testNegativeDurationValidation() throws JsonSchemaValidationException {
         "}")
     ));
 
-    JsonObject positiveDuration = new JsonObject().put("duration", "P3W");
-    JsonObject negativeDuration = new JsonObject().put("duration", "-P3W");
-    JsonObject positiveNullDuration = new JsonObject().put("duration", "P0W");
-    JsonObject negativeNullDuration = new JsonObject().put("duration", "-PT0S");
-
-    repository.validator("acceptable-duration.json").validate(positiveDuration).checkValidity();
-    repository.validator("acceptable-duration.json").validate(negativeDuration).checkValidity();
-    repository.validator("acceptable-duration.json").validate(positiveNullDuration).checkValidity();
-    try {
-      repository.validator("acceptable-duration.json").validate(negativeNullDuration).checkValidity();
-      fail("Should have thrown an exception");
-    } catch (JsonSchemaValidationException e) {
-      // OK
-    }
+    Consumer<String> shouldValidate = duration -> {
+      try {
+        repository.validator("acceptable-duration.json").validate(new JsonObject().put("duration", duration)).checkValidity();
+      } catch (JsonSchemaValidationException ignored) {
+        fail("Duration " + duration + " should pass validation.");
+      }
+    };
+
+    Consumer<String> shouldNotValidate = duration -> {
+      try {
+        repository.validator("acceptable-duration.json").validate(new JsonObject().put("duration", duration)).checkValidity();
+        fail("Duration " + duration + " should not pass validation.");
+      } catch (JsonSchemaValidationException ignored) {}
+    };
+
+    shouldValidate.accept("PT0S");
+    shouldValidate.accept("-PT0S");
+    shouldValidate.accept("PT-0S");
+    shouldValidate.accept("P1Y");
+    shouldValidate.accept("P1M");
+    shouldValidate.accept("P1W");
+    shouldValidate.accept("P1D");
+    shouldValidate.accept("PT1H");
+    shouldValidate.accept("PT1M");
+    shouldValidate.accept("PT1S");
+    shouldValidate.accept("P1Y2M");
+    shouldValidate.accept("P1M2W");
+    shouldValidate.accept("P1W2D");
+    shouldNotValidate.accept("P1M2Y");
+    shouldNotValidate.accept("P1W2M");
+    shouldNotValidate.accept("P1D2W");
+    shouldValidate.accept("PT1H2M");
+    shouldValidate.accept("PT1M2S");
+    shouldNotValidate.accept("PT1M2H");
+    shouldNotValidate.accept("PT1S2M");
+    shouldValidate.accept("P1Y2M3W4DT5H6M7S");
+    shouldValidate.accept("P-1Y-2M-3W-4DT-5H-6M-7S");
+    shouldValidate.accept("-P-1.0Y2.2M-33.4W-4.2DT5H-7S");
   }
 }