diff --git a/include/llvm/System/Program.h b/include/llvm/System/Program.h
index 7017305..0c14076 100644
--- a/include/llvm/System/Program.h
+++ b/include/llvm/System/Program.h
@@ -90,12 +90,13 @@
     /// @see Execute
     /// @brief Waits for the program to exit.
     int Wait
-    ( unsigned secondsToWait = 0, ///< If non-zero, this specifies the amount
+    ( const Path& path, ///< The path to the child process executable.
+      unsigned secondsToWait, ///< If non-zero, this specifies the amount
       ///< of time to wait for the child process to exit. If the time
       ///< expires, the child is killed and this call returns. If zero,
       ///< this function will wait until the child finishes or forever if
       ///< it doesn't.
-      std::string* ErrMsg = 0 ///< If non-zero, provides a pointer to a string
+      std::string* ErrMsg ///< If non-zero, provides a pointer to a string
       ///< instance in which error messages will be returned. If the string
       ///< is non-empty upon return an error occurred while waiting.
       );
diff --git a/lib/System/Program.cpp b/lib/System/Program.cpp
index cd58c2c..90aba76 100644
--- a/lib/System/Program.cpp
+++ b/lib/System/Program.cpp
@@ -31,7 +31,7 @@
                         std::string* ErrMsg) {
   Program prg;
   if (prg.Execute(path, args, envp, redirects, memoryLimit, ErrMsg))
-    return prg.Wait(secondsToWait, ErrMsg);
+    return prg.Wait(path, secondsToWait, ErrMsg);
   else
     return -1;
 }
diff --git a/lib/System/Unix/Program.inc b/lib/System/Unix/Program.inc
index 76012af..b92d080 100644
--- a/lib/System/Unix/Program.inc
+++ b/lib/System/Unix/Program.inc
@@ -228,12 +228,6 @@
   }
 #endif
 
-  if (!path.canExecute()) {
-    if (ErrMsg)
-      *ErrMsg = path.str() + " is not executable";
-    return false;
-  }
-
   // Create a child process.
   int child = fork();
   switch (child) {
@@ -297,7 +291,8 @@
 }
 
 int
-Program::Wait(unsigned secondsToWait,
+Program::Wait(const sys::Path &path,
+              unsigned secondsToWait,
               std::string* ErrMsg)
 {
 #ifdef HAVE_SYS_WAIT_H
@@ -355,6 +350,14 @@
   int result = 0;
   if (WIFEXITED(status)) {
     result = WEXITSTATUS(status);
+#ifdef HAVE_POSIX_SPAWN
+    // The posix_spawn child process returns 127 on any kind of error.
+    // Following the POSIX convention for command-line tools (which posix_spawn
+    // itself apparently does not), check to see if the failure was due to some
+    // reason other than the file not existing, and return 126 in this case.
+    if (result == 127 && path.exists())
+      result = 126;
+#endif
     if (result == 127) {
       *ErrMsg = llvm::sys::StrError(ENOENT);
       return -1;
diff --git a/lib/System/Win32/Program.inc b/lib/System/Win32/Program.inc
index ea1b5a6..b55aa2f 100644
--- a/lib/System/Win32/Program.inc
+++ b/lib/System/Win32/Program.inc
@@ -337,7 +337,8 @@
 }
 
 int
-Program::Wait(unsigned secondsToWait,
+Program::Wait(const Path &path,
+              unsigned secondsToWait,
               std::string* ErrMsg) {
   if (Data_ == 0) {
     MakeErrMsg(ErrMsg, "Process not started!");