diff --git a/Source/script.cpp b/Source/script.cpp
index fe5174d1..b70a0e39 100644
--- a/Source/script.cpp
+++ b/Source/script.cpp
@@ -4128,33 +4128,32 @@ int CEXEBuild::doCommand(int which_token, LineParser &line)
     return add_entry(&ent);
     case TOK_SETOUTPATH:
       {
-        const TCHAR *op=line.gettoken_str(1);
+        const TCHAR *op=line.gettoken_str(1), *cmdname=_T("SetOutPath");
         if (!_tcscmp(op,_T("-"))) op=_T("$INSTDIR");
-
-        SCRIPT_MSG(_T("SetOutPath: \"%") NPRIs _T("\"\n"),op);
+        SCRIPT_MSG(_T("%") NPRIs _T(": \"%") NPRIs _T("\"\n"),cmdname,op);
         ent.which=EW_CREATEDIR;
         ent.offsets[0]=add_string(op);
         ent.offsets[1]=1;
-
         DefineInnerLangString(NLF_OUTPUT_DIR);
       }
     return add_entry(&ent);
     case TOK_CREATEDIR:
       {
+        const TCHAR *cmdname=_T("CreateDirectory");
         TCHAR out_path[NSIS_MAX_STRLEN], *p=line.gettoken_str(1);
-        if (*p == _T('-')) out_path[0]=0;
+        bool badpath=IsWindowsPathRelative(p) && _T('$') != *p; // ExeHead will have to deal with expanded $variables...
+        if (badpath)
+          ERROR_MSG(_T("%") NPRIs _T(": Relative paths not supported\n"),cmdname);
         else
         {
-          if (p[0] == _T('\\') && p[1] != _T('\\')) p++;
           my_strncpy(out_path,p,COUNTOF(out_path));
           p=CharPrev(out_path,out_path+_tcslen(out_path));
-          if (_T('\\') == *p || _T('/') == *p) *p=0; // remove trailing slash
+          if (IsAgnosticPathSeparator(*p)) *p=0; // remove trailing slash
         }
-        if (!*out_path) PRINTHELP()
-        SCRIPT_MSG(_T("CreateDirectory: \"%") NPRIs _T("\"\n"),out_path);
+        if (badpath || !*out_path) PRINTHELP()
+        SCRIPT_MSG(_T("%") NPRIs _T(": \"%") NPRIs _T("\"\n"),cmdname,out_path);
         ent.which=EW_CREATEDIR;
         ent.offsets[0]=add_string(out_path);
-
         DefineInnerLangString(NLF_CREATE_DIR);
       }
     return add_entry(&ent);
diff --git a/Source/util.cpp b/Source/util.cpp
index 270a883b..e8f976e6 100644
--- a/Source/util.cpp
+++ b/Source/util.cpp
@@ -718,6 +718,22 @@ tstring remove_file_extension(const tstring& path) {
   return get_string_prefix(path, _T("."));
 }
 
+static int PathGetDosDriveNumber(const TCHAR *p)
+{
+  // Note: Unlike PathGetDriveNumber(), we require a path separator after the colon.
+  if (p[0] && _T(':') == p[1] && IsAgnosticPathSeparator(p[2]))
+  {
+    const TCHAR loch = p[0]|32;
+    if (loch >= _T('a') && loch <= _T('z')) return loch - _T('a');
+  }
+  return -1;
+}
+bool IsWindowsPathRelative(const TCHAR *p)
+{
+  if (_T('\\') == p[0]) return _T('\\') != p[1]; // Current drive relative, not (unverified) UNC
+  return PathGetDosDriveNumber(p) < 0;
+}
+
 struct ToLower
 {
    TCHAR operator() (TCHAR c) const { return _totlower(c); }
diff --git a/Source/util.h b/Source/util.h
index d0cd9bce..a990334d 100644
--- a/Source/util.h
+++ b/Source/util.h
@@ -47,11 +47,12 @@ tstring get_dir_name(const tstring& path);
 tstring get_file_name(const tstring& path);
 tstring get_executable_dir(const TCHAR *argv0);
 tstring remove_file_extension(const tstring& path);
-tstring lowercase(const tstring&);
+inline bool IsAgnosticPathSeparator(const TCHAR c) { return _T('\\') == c || _T('/') == c; }
+bool IsWindowsPathRelative(const TCHAR *p);
 
+tstring lowercase(const tstring&);
 tstring get_string_prefix(const tstring& str, const tstring& separator);
 tstring get_string_suffix(const tstring& str, const tstring& separator);
-
 void RawTStrToASCII(const TCHAR*in,char*out,UINT maxcch);
 size_t ExpandoStrFmtVaList(wchar_t*Stack, size_t cchStack, wchar_t**ppMalloc, const wchar_t*FmtStr, va_list Args);