diff --git a/Sources/TSCBasic/FileSystem.swift b/Sources/TSCBasic/FileSystem.swift
index 982a8039..6ff7b3fb 100644
--- a/Sources/TSCBasic/FileSystem.swift
+++ b/Sources/TSCBasic/FileSystem.swift
@@ -493,8 +493,7 @@ private struct LocalFileSystem: FileSystem {
 
     func readFileContents(_ path: AbsolutePath) throws -> ByteString {
         // Open the file.
-        let fp = fopen(path.pathString, "rb")
-        if fp == nil {
+        guard let fp = fopen(path.pathString, "rb") else {
             throw FileSystemError(errno: errno, path)
         }
         defer { fclose(fp) }
@@ -523,8 +522,7 @@ private struct LocalFileSystem: FileSystem {
 
     func writeFileContents(_ path: AbsolutePath, bytes: ByteString) throws {
         // Open the file.
-        let fp = fopen(path.pathString, "wb")
-        if fp == nil {
+        guard let fp = fopen(path.pathString, "wb") else {
             throw FileSystemError(errno: errno, path)
         }
         defer { fclose(fp) }
diff --git a/Sources/TSCBasic/Process.swift b/Sources/TSCBasic/Process.swift
index 6c8aa117..89d3a5be 100644
--- a/Sources/TSCBasic/Process.swift
+++ b/Sources/TSCBasic/Process.swift
@@ -144,6 +144,9 @@ public final class Process {
 
         /// The current OS does not support the workingDirectory API.
         case workingDirectoryNotSupported
+
+        /// The stdin could not be opened.
+        case stdinUnavailable
     }
 
     public enum OutputRedirection {
@@ -677,7 +680,10 @@ public final class Process {
         var stdinPipe: [Int32] = [-1, -1]
         try open(pipe: &stdinPipe)
 
-        let stdinStream = try LocalFileOutputByteStream(filePointer: fdopen(stdinPipe[1], "wb"), closeOnDeinit: true)
+        guard let fp = fdopen(stdinPipe[1], "wb") else {
+            throw Process.Error.stdinUnavailable
+        }
+        let stdinStream = try LocalFileOutputByteStream(filePointer: fp, closeOnDeinit: true)
 
         // Dupe the read portion of the remote to 0.
         posix_spawn_file_actions_adddup2(&fileActions, stdinPipe[0], 0)
@@ -1258,6 +1264,8 @@ extension Process.Error: CustomStringConvertible {
             return "could not find executable for '\(program)'"
         case .workingDirectoryNotSupported:
             return "workingDirectory is not supported in this platform"
+        case .stdinUnavailable:
+            return "could not open stdin on this platform"
         }
     }
 }
diff --git a/Sources/TSCBasic/WritableByteStream.swift b/Sources/TSCBasic/WritableByteStream.swift
index aee907e3..5b6e4c2c 100644
--- a/Sources/TSCBasic/WritableByteStream.swift
+++ b/Sources/TSCBasic/WritableByteStream.swift
@@ -790,7 +790,7 @@ public final class LocalFileOutputByteStream: FileOutputByteStream {
     override final func writeImpl(_ bytes: ArraySlice<UInt8>) {
         bytes.withUnsafeBytes { bytesPtr in
             while true {
-                let n = fwrite(bytesPtr.baseAddress, 1, bytesPtr.count, filePointer)
+                let n = fwrite(bytesPtr.baseAddress!, 1, bytesPtr.count, filePointer)
                 if n < 0 {
                     if errno == EINTR { continue }
                     errorDetected(code: errno)
diff --git a/Sources/TSCTestSupport/PseudoTerminal.swift b/Sources/TSCTestSupport/PseudoTerminal.swift
index 59610b61..2797c719 100644
--- a/Sources/TSCTestSupport/PseudoTerminal.swift
+++ b/Sources/TSCTestSupport/PseudoTerminal.swift
@@ -24,7 +24,7 @@ public final class PseudoTerminal {
         if openpty(&primary, &secondary, nil, nil, nil) != 0 {
             return nil
         }
-        guard let outStream = try? LocalFileOutputByteStream(filePointer: fdopen(secondary, "w"), closeOnDeinit: false) else {
+        guard let outStream = try? LocalFileOutputByteStream(filePointer: fdopen(secondary, "w")!, closeOnDeinit: false) else {
             return nil
         }
         self.outStream = outStream
diff --git a/Tests/TSCBasicTests/PathShimTests.swift b/Tests/TSCBasicTests/PathShimTests.swift
index 1af04a37..76fd6324 100644
--- a/Tests/TSCBasicTests/PathShimTests.swift
+++ b/Tests/TSCBasicTests/PathShimTests.swift
@@ -39,7 +39,7 @@ class WalkTests : XCTestCase {
         var expected: [AbsolutePath] = [
             "\(root)/usr",
             "\(root)/bin",
-            "\(root)/xbin"
+            "\(root)/etc"
         ]
       #else
         let root = ""