diff --git a/Sources/EvolutionMetadataExtraction/CommandLineSupport.swift b/Sources/EvolutionMetadataExtraction/CommandLineSupport.swift
index 435e573..3ab73cd 100644
--- a/Sources/EvolutionMetadataExtraction/CommandLineSupport.swift
+++ b/Sources/EvolutionMetadataExtraction/CommandLineSupport.swift
@@ -128,7 +128,7 @@ public enum ArgumentValidation {
                 for arg in forceExtract {
                     if arg == "all" {
                         forceAll = true
-                    } else if arg.contains(/^SE-\d\d\d\d$/){
+                    } else if arg.contains(/^SE-\d{4}/){
                         forcedExtractionIDs.append(arg)
                     } else {
                         throw ValidationError("Valid --force-extraction values are 'all' and proposal ids of the form 'SE-NNNN'")
diff --git a/Sources/EvolutionMetadataExtraction/ExtractionJob.swift b/Sources/EvolutionMetadataExtraction/ExtractionJob.swift
index b1098b2..1e53323 100644
--- a/Sources/EvolutionMetadataExtraction/ExtractionJob.swift
+++ b/Sources/EvolutionMetadataExtraction/ExtractionJob.swift
@@ -178,8 +178,9 @@ extension ExtractionJob {
         return ExtractionJob(project: project, output: output, snapshot: snapshot, proposalSpecs: proposalSpecs, previousResults: nil, forcedExtractionIDs: forcedExtractionIDs, jobMetadata: jobMetadata)
     }
 
-    static func previousResults(from url: URL, ignorePreviousResults: Bool) async throws -> EvolutionMetadata? {
+    static func previousResults(from url: URL?, ignorePreviousResults: Bool) async throws -> EvolutionMetadata? {
         if ignorePreviousResults { return nil }
+        guard let url else { return nil }
 
         let data: Data?
         if url.isFileURL {
diff --git a/Sources/EvolutionMetadataExtraction/Extractors/FieldExtractors/PreviousProposalExtractor.swift b/Sources/EvolutionMetadataExtraction/Extractors/FieldExtractors/PreviousProposalExtractor.swift
index 7833cbd..07c9184 100644
--- a/Sources/EvolutionMetadataExtraction/Extractors/FieldExtractors/PreviousProposalExtractor.swift
+++ b/Sources/EvolutionMetadataExtraction/Extractors/FieldExtractors/PreviousProposalExtractor.swift
@@ -36,7 +36,7 @@ struct PreviousProposalExtractor: MarkupWalker, ValueExtractor {
     
     mutating func visitText(_ text: Text) -> () {
         // VALIDATION ENHANCEMENT: Potentially look for missing links or text that does not include a proposal ID
-        for match in text.string.matches(of: /SE-\d\d\d\d/) {
+        for match in text.string.matches(of: /SE-\d{4}/) {
             _previousProposalIDs.append(String(match.0))
         }
     }
diff --git a/Sources/EvolutionMetadataExtraction/Extractors/FieldExtractors/ProposalLinkExtractor.swift b/Sources/EvolutionMetadataExtraction/Extractors/FieldExtractors/ProposalLinkExtractor.swift
index ac9070c..fb0c2a6 100644
--- a/Sources/EvolutionMetadataExtraction/Extractors/FieldExtractors/ProposalLinkExtractor.swift
+++ b/Sources/EvolutionMetadataExtraction/Extractors/FieldExtractors/ProposalLinkExtractor.swift
@@ -43,7 +43,7 @@ struct ProposalLinkExtractor: MarkupWalker, ValueExtractor {
                 }
 
                 // The link should be relative and contain the correct number of digits.
-                if !proposalLink.destination.contains(/^\d\d\d\d-.*\.md$/) {
+                if !proposalLink.destination.contains(/^\d{4}-.*\.md$/) {
                     self.proposalLink?.destination = "" // Do not include an incorrect destination
                     issues.reportIssue(Proposal.Issue.invalidProposalIDLink, source: source)
                 }
diff --git a/Sources/EvolutionMetadataExtraction/Utilities/Project.swift b/Sources/EvolutionMetadataExtraction/Utilities/Project.swift
index 804cd2d..7c35ce8 100644
--- a/Sources/EvolutionMetadataExtraction/Utilities/Project.swift
+++ b/Sources/EvolutionMetadataExtraction/Utilities/Project.swift
@@ -22,14 +22,14 @@ public final class Project: Sendable {
     let path: String
     let proposalPrefix: String
     nonisolated(unsafe) let proposalRegex: Regex<Substring>
-    let previousResultsURL: URL
+    let previousResultsURL: URL?
     let defaultOutputFilename: String
     private let endpointBaseURL: URL
     let mainBranchEndpoint: URL
     let proposalListingEndpoint: URL
     let validationExemptions: [Int:RangeSet<Int>]
     
-    private init(name: String, organization: String, repository: String, path: String, proposalPrefix: String, proposalRegex: Regex<Substring>, previousResultsURL: URL, defaultOutputFilename: String, validationExemptions: [Int:RangeSet<Int>]) {
+    private init(name: String, organization: String, repository: String, path: String, proposalPrefix: String, proposalRegex: Regex<Substring>, previousResultsURL: URL?, defaultOutputFilename: String, validationExemptions: [Int:RangeSet<Int>]) {
         self.name = name
         self.organization = organization
         self.repository = repository
@@ -60,7 +60,7 @@ public final class Project: Sendable {
         repository: "swift-evolution",
         path: "proposals",
         proposalPrefix: "SE",
-        proposalRegex: /^SE-\d\d\d\d$/,
+        proposalRegex: /^SE-\d{4}$/,
         previousResultsURL: URL(string: "https://download.swift.org/swift-evolution/v1/evolution.json")!,
         defaultOutputFilename: "evolution.json",
         validationExemptions: [
@@ -90,8 +90,8 @@ public final class Project: Sendable {
         repository: "swift-evolution",
         path: "proposals/testing",
         proposalPrefix: "ST",
-        proposalRegex: /^ST-\d\d\d\d$/,
-        previousResultsURL: URL(string: "https://download.swift.org/swift-evolution/v1/testing-evolution.json")!,
+        proposalRegex: /^ST-\d{4}$/,
+        previousResultsURL: nil, // URL(string: "https://download.swift.org/swift-evolution/v1/testing-evolution.json")!,
         defaultOutputFilename: "testing-evolution.json",
         validationExemptions: [
             // Early proposals did not have a review manager
@@ -106,8 +106,8 @@ public final class Project: Sendable {
         repository: "swift-foundation",
         path: "Proposals",
         proposalPrefix: "SF",
-        proposalRegex: /^SF-\d\d\d\d$/,
-        previousResultsURL: URL(string: "https://download.swift.org/swift-evolution/v1/foundation-evolution.json")!,
+        proposalRegex: /^SF-\d{4}$/,
+        previousResultsURL: nil, // URL(string: "https://download.swift.org/swift-evolution/v1/foundation-evolution.json")!,
         defaultOutputFilename: "foundation-evolution.json",
         validationExemptions: [:]
     )