diff --git a/tests/bugfixes/redmine/test_issue_1108.py b/tests/bugfixes/redmine/test_issue_1108.py
index 7801b52199..0bed6d3427 100644
--- a/tests/bugfixes/redmine/test_issue_1108.py
+++ b/tests/bugfixes/redmine/test_issue_1108.py
@@ -159,7 +159,7 @@ class CheckDumpSubFiles(metaclass=system_tests.CaseMeta):
        2 |     120 | Caption                  |     12 | Classic View
    17987 | 0xffd9 EOI  
 """,
-    """STRUCTURE OF PNG FILE: """ + filenames[1] + """
+    """STRUCTURE OF PNG FILE: """ + filenames[1] + r"""
  address | chunk |  length | data                           | checksum
        8 | IHDR  |      13 | ...@........                   | 0x7f775da4
       33 | iCCP  |    1404 | icc..x...i8........af\...w_3.. | 0x363e2409
diff --git a/tests/bugfixes/redmine/test_issue_662.py b/tests/bugfixes/redmine/test_issue_662.py
index b335cb9e04..a10132aacf 100644
--- a/tests/bugfixes/redmine/test_issue_662.py
+++ b/tests/bugfixes/redmine/test_issue_662.py
@@ -100,7 +100,7 @@ class UnicodeEncodingOfExifUserCommentTag(metaclass=system_tests.CaseMeta):
 
 """,
         "",
-        """ExifTag                    
+        r"""ExifTag                    
   0000  1a 00 00 00                                      ....
 
 UserComment                
diff --git a/tests/bugfixes/redmine/test_issue_922.py b/tests/bugfixes/redmine/test_issue_922.py
index db0b332ef4..03ea6550bd 100644
--- a/tests/bugfixes/redmine/test_issue_922.py
+++ b/tests/bugfixes/redmine/test_issue_922.py
@@ -127,7 +127,7 @@ class AddMinusPSOption(metaclass=CaseMeta):
                                                                                                     
                            
 <?xpacket end="w"?>""",
-        """STRUCTURE OF PNG FILE: $png_bug_file
+        r"""STRUCTURE OF PNG FILE: $png_bug_file
  address | chunk |  length | data                           | checksum
        8 | IHDR  |      13 | ...@........                   | 0x7f775da4
       33 | zTXt  |    8769 | Raw profile type exif..x...[r. | 0x4a89d860