diff --git a/source/JSONSchema-Core-Tests/JSONSchemaTests.class.st b/source/JSONSchema-Core-Tests/JSONSchemaTests.class.st
index c83e3d0..0cbe3cd 100644
--- a/source/JSONSchema-Core-Tests/JSONSchemaTests.class.st
+++ b/source/JSONSchema-Core-Tests/JSONSchemaTests.class.st
@@ -5,6 +5,20 @@ Class {
 	#package : 'JSONSchema-Core-Tests'
 }
 
+{ #category : 'tests' }
+JSONSchemaTests >> testAdditionalPropertiesFalseEnforcedWithoutPatternProperties [
+	"Regression: JSONSchemaPatternPropertiesConstraint (the constraint that enforces
+	additionalProperties) only activated when patternProperties was present -
+	validate:'s own logic already handled the no-patternProperties case correctly, it
+	just never got attached. A properties-only schema with additionalProperties:false
+	silently accepted extra properties. Found 2026-08-02 via the RecurringEvents schema
+	(schema/recurring-events.schema.json)."
+	| schema |
+	schema := JSONSchema fromString: '{"type":"object","properties":{"foo":{"type":"string"}},"required":["foo"],"additionalProperties":false}'.
+	self shouldnt: [ schema validate: {'foo'->'bar'} asDictionary ] raise: Error.
+	self should: [ schema validate: {'foo'->'bar'. 'extra'->1} asDictionary ] raise: JSONTypeError
+]
+
 { #category : 'tests' }
 JSONSchemaTests >> testAllOfCompositionMergesRequiredAcrossBranches [
 	| definition schema |
@@ -281,3 +295,21 @@ JSONSchemaTests >> testSimpleObjectSchema [
 	self assert: object foo equals: '123'.
 	self assert: object bar equals: 123
 ]
+
+{ #category : 'tests' }
+JSONSchemaTests >> testValidateAcceptsValidDateTimeStringOnExplicitlyTypedSchema [
+	"Regression: JSONPrimitiveSchema>>validate: (a leftover from before the generic
+	JSONSchemaFormatConstraint - Tier G - existed) called the format class's own
+	validate: with the raw JSON string. JSONFormatDateTime/JSONFormatDate/JSONFormatURI's
+	class-side validate: expect an already-converted value (DateAndTime/Date/ZnUrl, as
+	produced by the read: pipeline), so this crashed with a bogus JSONTypeError for
+	*every* valid date-time/date/uri string whenever type was explicit alongside
+	format - JSONSchemaFormatConstraint's own validateString: (which does the real,
+	correct check against the raw string) already covers this generically, making the
+	call redundant as well as wrong. Found 2026-08-02 via the RecurringEvents schema,
+	where e.g. dateAndTime declares type:string/format:date-time for its at property."
+	| schema |
+	schema := JSONSchema fromString: '{"type":"string","format":"date-time"}'.
+	self shouldnt: [ schema validate: '2026-01-01T00:00:00Z' ] raise: Error.
+	self should: [ schema validate: 'not-a-date' ] raise: JSONConstraintError
+]
diff --git a/source/JSONSchema-Core/JSONPrimitiveSchema.class.st b/source/JSONSchema-Core/JSONPrimitiveSchema.class.st
index 72b7407..87190d0 100644
--- a/source/JSONSchema-Core/JSONPrimitiveSchema.class.st
+++ b/source/JSONSchema-Core/JSONPrimitiveSchema.class.st
@@ -141,10 +141,7 @@ JSONPrimitiveSchema >> schema: aSchema [
 
 { #category : 'validation' }
 JSONPrimitiveSchema >> validate: anObject [
-	super validate: anObject.
-	format ifNotNil: [ 
-		format validate: anObject ]
-	
+	super validate: anObject
 ]
 
 { #category : 'writing' }
diff --git a/source/JSONSchema-Core/JSONSchemaPatternPropertiesConstraint.class.st b/source/JSONSchema-Core/JSONSchemaPatternPropertiesConstraint.class.st
index 341565e..fb44046 100644
--- a/source/JSONSchema-Core/JSONSchemaPatternPropertiesConstraint.class.st
+++ b/source/JSONSchema-Core/JSONSchemaPatternPropertiesConstraint.class.st
@@ -24,7 +24,11 @@ JSONSchemaPatternPropertiesConstraint >> initializeFromDefinition: aDefinition [
 
 { #category : 'validation' }
 JSONSchemaPatternPropertiesConstraint >> validate [
-	^ patternProperties notNil
+	"Active whenever there is something to enforce beyond the schema's own declared
+	properties: either patternProperties itself, or a restricting additionalProperties
+	(false, or a schema) - the properties-only case (no patternProperties) still needs
+	this constraint to enforce additionalProperties."
+	^ patternProperties notNil or: [ additionalProperties notNil and: [ additionalProperties ~= true ] ]
 ]
 
 { #category : 'validation' }
@@ -33,10 +37,13 @@ JSONSchemaPatternPropertiesConstraint >> validate: aDictionary [
 	whose regex matches the name (unanchored search). A name is 'covered' if it is
 	in properties or matched at least one pattern; names covered by neither are
 	validated against additionalProperties when that is an actual schema (the default
-	is Boolean true = accept all)."
+	is Boolean true = accept all). patternProperties may be nil - a schema can declare
+	only properties/additionalProperties with no patternProperties at all."
 	| resolvedPatterns |
-	resolvedPatterns := patternProperties associations collect: [ :assoc |
-		{ assoc key asECMARegex. self resolveVisitor visitSchemaSpec: assoc value } ].
+	resolvedPatterns := patternProperties
+		ifNil: [ #() ]
+		ifNotNil: [ patternProperties associations collect: [ :assoc |
+			{ assoc key asECMARegex. self resolveVisitor visitSchemaSpec: assoc value } ] ].
 	aDictionary keysAndValuesDo: [ :key :value |
 		| matchedPattern |
 		matchedPattern := false.
diff --git a/source/JSONSchema-Testsuite-Tests/JSONSchemaAdditionalPropertiesAllowsASchemaWhichShouldValidateTests.class.st b/source/JSONSchema-Testsuite-Tests/JSONSchemaAdditionalPropertiesAllowsASchemaWhichShouldValidateTests.class.st
index 0232c98..8175793 100644
--- a/source/JSONSchema-Testsuite-Tests/JSONSchemaAdditionalPropertiesAllowsASchemaWhichShouldValidateTests.class.st
+++ b/source/JSONSchema-Testsuite-Tests/JSONSchemaAdditionalPropertiesAllowsASchemaWhichShouldValidateTests.class.st
@@ -6,11 +6,6 @@ Class {
 	#tag : 'AdditionalProperties'
 }
 
-{ #category : 'testing' }
-JSONSchemaAdditionalPropertiesAllowsASchemaWhichShouldValidateTests >> expectedFailures [
-	^ #(#testAnAdditionalInvalidPropertyIsInvalid)
-]
-
 { #category : 'accessing' }
 JSONSchemaAdditionalPropertiesAllowsASchemaWhichShouldValidateTests >> schemaString [
 	^ '{"properties":{"foo":{},"bar":{}},"additionalProperties":{"type":"boolean"}}'
diff --git a/source/JSONSchema-Testsuite-Tests/JSONSchemaAdditionalPropertiesCanExistByItselfTests.class.st b/source/JSONSchema-Testsuite-Tests/JSONSchemaAdditionalPropertiesCanExistByItselfTests.class.st
index 418c28c..7e9ebc6 100644
--- a/source/JSONSchema-Testsuite-Tests/JSONSchemaAdditionalPropertiesCanExistByItselfTests.class.st
+++ b/source/JSONSchema-Testsuite-Tests/JSONSchemaAdditionalPropertiesCanExistByItselfTests.class.st
@@ -6,11 +6,6 @@ Class {
 	#tag : 'AdditionalProperties'
 }
 
-{ #category : 'testing' }
-JSONSchemaAdditionalPropertiesCanExistByItselfTests >> expectedFailures [
-	^ #(#testAnAdditionalInvalidPropertyIsInvalid)
-]
-
 { #category : 'accessing' }
 JSONSchemaAdditionalPropertiesCanExistByItselfTests >> schemaString [
 	^ '{"additionalProperties":{"type":"boolean"}}'
diff --git a/source/JSONSchema-Testsuite-Tests/JSONSchemaAdditionalPropertiesShouldNotLookInApplicatorsTests.class.st b/source/JSONSchema-Testsuite-Tests/JSONSchemaAdditionalPropertiesShouldNotLookInApplicatorsTests.class.st
index df26ca1..b7f5097 100644
--- a/source/JSONSchema-Testsuite-Tests/JSONSchemaAdditionalPropertiesShouldNotLookInApplicatorsTests.class.st
+++ b/source/JSONSchema-Testsuite-Tests/JSONSchemaAdditionalPropertiesShouldNotLookInApplicatorsTests.class.st
@@ -6,11 +6,6 @@ Class {
 	#tag : 'AdditionalProperties'
 }
 
-{ #category : 'testing' }
-JSONSchemaAdditionalPropertiesShouldNotLookInApplicatorsTests >> expectedFailures [
-	^ #(#testPropertiesDefinedInAllOfAreNotExamined)
-]
-
 { #category : 'accessing' }
 JSONSchemaAdditionalPropertiesShouldNotLookInApplicatorsTests >> schemaString [
 	^ '{"allOf":[{"properties":{"foo":{}}}],"additionalProperties":{"type":"boolean"}}'