diff --git a/dll/win32/shlwapi/path.c b/dll/win32/shlwapi/path.c
index c26263152df..09acc200e12 100644
--- a/dll/win32/shlwapi/path.c
+++ b/dll/win32/shlwapi/path.c
@@ -4061,31 +4061,23 @@ LPCWSTR WINAPI PathFindSuffixArrayW(LPCWSTR lpszSuffix, LPCWSTR *lppszArray, int
  * NOTES
  *  A decorations form is "path[n].ext" where "n" is an optional decimal number.
  */
-VOID WINAPI PathUndecorateA(LPSTR lpszPath)
+void WINAPI PathUndecorateA(LPSTR pszPath)
 {
-  TRACE("(%s)\n",debugstr_a(lpszPath));
+  char *ext, *skip;
 
-  if (lpszPath)
-  {
-    LPSTR lpszExt = PathFindExtensionA(lpszPath);
-    if (lpszExt > lpszPath && lpszExt[-1] == ']')
-    {
-      LPSTR lpszSkip = lpszExt - 2;
-      if (*lpszSkip == '[')
-        lpszSkip++;  /* [] (no number) */
-      else
-        while (lpszSkip > lpszPath && isdigit(lpszSkip[-1]))
-          lpszSkip--;
-      if (lpszSkip > lpszPath && lpszSkip[-1] == '[' && lpszSkip[-2] != '\\')
-      {
-        /* remove the [n] */
-        lpszSkip--;
-        while (*lpszExt)
-          *lpszSkip++ = *lpszExt++;
-        *lpszSkip = '\0';
-      }
-    }
-  }
+  TRACE("(%s)\n", debugstr_a(pszPath));
+
+  if (!pszPath) return;
+
+  ext = PathFindExtensionA(pszPath);
+  if (ext == pszPath || ext[-1] != ']') return;
+
+  skip = ext - 2;
+  while (skip > pszPath && '0' <= *skip && *skip <= '9')
+      skip--;
+
+  if (skip > pszPath && *skip == '[' && skip[-1] != '\\')
+      memmove(skip, ext, strlen(ext) + 1);
 }
 
 /*************************************************************************
@@ -4093,31 +4085,23 @@ VOID WINAPI PathUndecorateA(LPSTR lpszPath)
  *
  * See PathUndecorateA.
  */
-VOID WINAPI PathUndecorateW(LPWSTR lpszPath)
+void WINAPI PathUndecorateW(LPWSTR pszPath)
 {
-  TRACE("(%s)\n",debugstr_w(lpszPath));
+  WCHAR *ext, *skip;
 
-  if (lpszPath)
-  {
-    LPWSTR lpszExt = PathFindExtensionW(lpszPath);
-    if (lpszExt > lpszPath && lpszExt[-1] == ']')
-    {
-      LPWSTR lpszSkip = lpszExt - 2;
-      if (*lpszSkip == '[')
-        lpszSkip++; /* [] (no number) */
-      else
-        while (lpszSkip > lpszPath && isdigitW(lpszSkip[-1]))
-          lpszSkip--;
-      if (lpszSkip > lpszPath && lpszSkip[-1] == '[' && lpszSkip[-2] != '\\')
-      {
-        /* remove the [n] */
-        lpszSkip--;
-        while (*lpszExt)
-          *lpszSkip++ = *lpszExt++;
-        *lpszSkip = '\0';
-      }
-    }
-  }
+  TRACE("(%s)\n", debugstr_w(pszPath));
+
+  if (!pszPath) return;
+
+  ext = PathFindExtensionW(pszPath);
+  if (ext == pszPath || ext[-1] != ']') return;
+
+  skip = ext - 2;
+  while (skip > pszPath && '0' <= *skip && *skip <= '9')
+      skip--;
+
+  if (skip > pszPath && *skip == '[' && skip[-1] != '\\')
+      memmove(skip, ext, (wcslen(ext) + 1) * sizeof(WCHAR));
 }
 
 /*************************************************************************
diff --git a/modules/rostests/winetests/shlwapi/path.c b/modules/rostests/winetests/shlwapi/path.c
index 4a6fbd91f6d..c5142b992aa 100644
--- a/modules/rostests/winetests/shlwapi/path.c
+++ b/modules/rostests/winetests/shlwapi/path.c
@@ -1672,6 +1672,46 @@ static void test_PathStripPathA(void)
     PathStripPathA((char*)const_path);
 }
 
+static void test_PathUndecorate(void)
+{
+    static const struct {
+        const WCHAR *path;
+        const WCHAR *expect;
+    } tests[] = {
+        { L"c:\\test\\a[123]",          L"c:\\test\\a" },
+        { L"c:\\test\\a[123].txt",      L"c:\\test\\a.txt" },
+        { L"c:\\test\\a.txt[123]",      L"c:\\test\\a.txt[123]" },
+        { L"c:\\test\\a[123a].txt",     L"c:\\test\\a[123a].txt" },
+        { L"c:\\test\\a[a123].txt",     L"c:\\test\\a[a123].txt" },
+        { L"c:\\test\\a[12\x0660].txt", L"c:\\test\\a[12\x0660].txt" },
+        { L"c:\\test\\a[12]file",       L"c:\\test\\a[12]file" },
+        { L"c:\\test[123]\\a",          L"c:\\test[123]\\a" },
+        { L"c:\\test\\[123]",           L"c:\\test\\[123]" },
+        { L"a[123]",                    L"a" },
+        { L"a[]",                       L"a" },
+        { L"[123]",                     L"[123]" }
+    };
+    char bufa[MAX_PATH], expect[MAX_PATH];
+    WCHAR buf[MAX_PATH];
+    unsigned i;
+
+    for (i = 0; i < ARRAY_SIZE(tests); i++)
+    {
+        wcscpy(buf, tests[i].path);
+        PathUndecorateW(buf);
+        ok(!wcscmp(buf, tests[i].expect), "PathUndecorateW returned %s, expected %s\n",
+           wine_dbgstr_w(buf), wine_dbgstr_w(tests[i].expect));
+
+        WideCharToMultiByte(CP_ACP, WC_NO_BEST_FIT_CHARS, tests[i].path, -1, bufa, ARRAY_SIZE(bufa), "?", NULL);
+        WideCharToMultiByte(CP_ACP, WC_NO_BEST_FIT_CHARS, tests[i].expect, -1, expect, ARRAY_SIZE(expect), "?", NULL);
+        PathUndecorateA(bufa);
+        ok(!strcmp(bufa, expect), "PathUndecorateA returned %s, expected %s\n", bufa, expect);
+    }
+
+    PathUndecorateA(NULL);
+    PathUndecorateW(NULL);
+}
+
 START_TEST(path)
 {
     HMODULE hShlwapi = GetModuleHandleA("shlwapi.dll");
@@ -1718,4 +1758,5 @@ START_TEST(path)
     test_PathIsRelativeA();
     test_PathIsRelativeW();
     test_PathStripPathA();
+    test_PathUndecorate();
 }