diff --git a/dlls/ntdll/exception.c b/dlls/ntdll/exception.c
index 59177b77c79..8286c9dcd52 100644
--- a/dlls/ntdll/exception.c
+++ b/dlls/ntdll/exception.c
@@ -346,3 +346,47 @@ void __wine_spec_unimplemented_stub( const char *module, const char *function )
     record.ExceptionInformation[1] = (ULONG_PTR)function;
     for (;;) RtlRaiseException( &record );
 }
+
+
+/*************************************************************
+ *            IsBadStringPtrA
+ *
+ * IsBadStringPtrA replacement for ntdll, to catch exception in debug traces.
+ */
+BOOL WINAPI IsBadStringPtrA( LPCSTR str, UINT_PTR max )
+{
+    if (!str) return TRUE;
+    __TRY
+    {
+        volatile const char *p = str;
+        while (p != str + max) if (!*p++) break;
+    }
+    __EXCEPT_PAGE_FAULT
+    {
+        return TRUE;
+    }
+    __ENDTRY
+    return FALSE;
+}
+
+
+/*************************************************************
+ *            IsBadStringPtrW
+ *
+ * IsBadStringPtrW replacement for ntdll, to catch exception in debug traces.
+ */
+BOOL WINAPI IsBadStringPtrW( LPCWSTR str, UINT_PTR max )
+{
+    if (!str) return TRUE;
+    __TRY
+    {
+        volatile const WCHAR *p = str;
+        while (p != str + max) if (!*p++) break;
+    }
+    __EXCEPT_PAGE_FAULT
+    {
+        return TRUE;
+    }
+    __ENDTRY
+    return FALSE;
+}
diff --git a/include/wine/debug.h b/include/wine/debug.h
index c7eb185257f..bb728270593 100644
--- a/include/wine/debug.h
+++ b/include/wine/debug.h
@@ -24,9 +24,7 @@
 #include <stdarg.h>
 #include <stdio.h>
 #include <windef.h>
-#ifndef _NTSYSTEM_
 #include <winbase.h>
-#endif
 #ifndef GUID_DEFINED
 #include <guiddef.h>
 #endif
@@ -227,9 +225,7 @@ static inline const char *wine_dbgstr_an( const char *str, int n )
 
     if (!str) return "(null)";
     if (!((ULONG_PTR)str >> 16)) return wine_dbg_sprintf( "#%04x", LOWORD(str) );
-#ifndef _NTSYSTEM_
     if (IsBadStringPtrA( str, n )) return "(invalid)";
-#endif
     if (n == -1) for (n = 0; str[n]; n++) ;
     *dst++ = '"';
     while (n-- > 0 && dst <= buffer + sizeof(buffer) - 9)
@@ -271,9 +267,7 @@ static inline const char *wine_dbgstr_wn( const WCHAR *str, int n )
 
     if (!str) return "(null)";
     if (!((ULONG_PTR)str >> 16)) return wine_dbg_sprintf( "#%04x", LOWORD(str) );
-#ifndef _NTSYSTEM_
     if (IsBadStringPtrW( str, n )) return "(invalid)";
-#endif
     if (n == -1) for (n = 0; str[n]; n++) ;
     *dst++ = 'L';
     *dst++ = '"';