diff --git a/dll/win32/setupapi/devinst.c b/dll/win32/setupapi/devinst.c
index d0de498923b..93fbd819b52 100644
--- a/dll/win32/setupapi/devinst.c
+++ b/dll/win32/setupapi/devinst.c
@@ -2689,6 +2689,7 @@ HKEY WINAPI SetupDiCreateDeviceInterfaceRegKeyW(
         if (SymbolicLink[Index] == L'}' && SymbolicLink[Index + 1] == L'\\')
         {
             /* Found it */
+            SymbolicLink[Index + 1] = L'#';
             break;
         }
         /* Replace all '\' backslashes by '#' pounds in symbolic link */
@@ -2709,8 +2710,7 @@ HKEY WINAPI SetupDiCreateDeviceInterfaceRegKeyW(
         return INVALID_HANDLE_VALUE;
     }
 
-    ReferenceString[0] = L'#';
-    wcscpy(ReferenceString + 1, &SymbolicLink[Index + 2]); /* Skip first '\' backslash */
+    wcscpy(ReferenceString, &SymbolicLink[Index + 1]);
 
     /* Null-terminate symbolic link at the beginning of the reference part,
      * as we don't need a ref part in key name. */
@@ -2744,17 +2744,19 @@ HKEY WINAPI SetupDiCreateDeviceInterfaceRegKeyW(
     {
         if (InfHandle && InfSectionName)
         {
-            if (!SetupInstallFromInfSection(NULL /*FIXME */,
-                                            InfHandle,
-                                            InfSectionName,
-                                            SPINST_INIFILES | SPINST_REGISTRY | SPINST_INI2REG | SPINST_FILES | SPINST_BITREG | SPINST_REGSVR | SPINST_UNREGSVR | SPINST_PROFILEITEMS | SPINST_COPYINF,
-                                            hDevParamKey,
-                                            NULL,
-                                            0,
-                                            set->SelectedDevice->InstallParams.InstallMsgHandler,
-                                            set->SelectedDevice->InstallParams.InstallMsgHandlerContext,
-                                            INVALID_HANDLE_VALUE,
-                                            NULL))
+            if (!SetupInstallFromInfSectionW(NULL /*FIXME */,
+                                             InfHandle,
+                                             InfSectionName,
+                                             SPINST_INIFILES | SPINST_REGISTRY | SPINST_INI2REG |
+                                                 SPINST_FILES | SPINST_BITREG | SPINST_REGSVR |
+                                                 SPINST_UNREGSVR | SPINST_PROFILEITEMS | SPINST_COPYINF,
+                                             hDevParamKey,
+                                             NULL,
+                                             0,
+                                             set->SelectedDevice->InstallParams.InstallMsgHandler,
+                                             set->SelectedDevice->InstallParams.InstallMsgHandlerContext,
+                                             INVALID_HANDLE_VALUE,
+                                             NULL))
             {
                 RegCloseKey(hDevParamKey);
                 return INVALID_HANDLE_VALUE;
diff --git a/dll/win32/setupapi/interface.c b/dll/win32/setupapi/interface.c
index 4fe98c4cd4e..c167e0ad05c 100644
--- a/dll/win32/setupapi/interface.c
+++ b/dll/win32/setupapi/interface.c
@@ -301,35 +301,33 @@ CreateSymbolicLink(
     IN LPCWSTR ReferenceString,
     IN struct DeviceInfo *devInfo)
 {
-    DWORD Length, Index, Offset;
-    LPWSTR Key;
+    SIZE_T ActualLength, Length;
+    WCHAR GuidString[MAX_GUID_STRING_LEN];
+    LPWSTR SymbolicLink;
 
-    Length = wcslen(devInfo->instanceId) + 4 /* prepend ##?# */ + 41 /* #{GUID} + */ + 1 /* zero byte */;
+    Length = 4 + // "\\\\?\\"
+             wcslen(devInfo->instanceId) +
+             1 + (MAX_GUID_STRING_LEN - 1) + 1 + // "#{GUID}\\"
+             wcslen(ReferenceString) +
+             1; // UNICODE_NULL
 
-    Key = HeapAlloc(GetProcessHeap(), HEAP_ZERO_MEMORY, Length * sizeof(WCHAR));
-    if (!Key)
+    SymbolicLink = HeapAlloc(GetProcessHeap(), HEAP_ZERO_MEMORY, Length * sizeof(WCHAR));
+    if (!SymbolicLink)
         return NULL;
 
-    wcscpy(Key, L"##?#");
-    wcscat(Key, devInfo->instanceId);
+    pSetupStringFromGuid(InterfaceGuid, GuidString, ARRAYSIZE(GuidString));
 
-    for(Index = 4; Index < Length; Index++)
-    {
-        if (Key[Index] == L'\\')
-        {
-            Key[Index] = L'#';
-        }
-    }
+    ActualLength = swprintf(SymbolicLink,
+                            Length,
+                            L"\\\\?\\%s#%s\\%s",
+                            devInfo->instanceId,
+                            GuidString,
+                            ReferenceString);
+    ASSERT(ActualLength == Length - 1);
 
-    wcscat(Key, L"#");
-
-    Offset = wcslen(Key);
-    pSetupStringFromGuid(InterfaceGuid, Key + Offset, Length - Offset);
-
-    return Key;
+    return SymbolicLink;
 }
 
-
 static BOOL
 InstallOneInterface(
     IN LPGUID InterfaceGuid,