diff --git a/Doc/lib/libdoctest.tex b/Doc/lib/libdoctest.tex
index 0db5d5d91b6..dca79f7ab55 100644
--- a/Doc/lib/libdoctest.tex
+++ b/Doc/lib/libdoctest.tex
@@ -344,17 +344,17 @@ can also be used in doctest directives (see below).
     is prone to in regular expressions.
 \end{datadesc}
 
-\begin{datadesc}{UNIFIED_DIFF}
+\begin{datadesc}{REPORT_UDIFF}
     When specified, failures that involve multi-line expected and
     actual outputs are displayed using a unified diff.
 \end{datadesc}
 
-\begin{datadesc}{CONTEXT_DIFF}
+\begin{datadesc}{REPORT_CDIFF}
     When specified, failures that involve multi-line expected and
     actual outputs will be displayed using a context diff.
 \end{datadesc}
 
-\begin{datadesc}{NDIFF_DIFF}
+\begin{datadesc}{REPORT_NDIFF}
     When specified, differences are computed by \code{difflib.Differ},
     using the same algorithm as the popular \file{ndiff.py} utility.
     This is the only method that marks differences within lines as
@@ -421,8 +421,8 @@ can be useful.
 
 \versionchanged[Constants \constant{DONT_ACCEPT_BLANKLINE},
     \constant{NORMALIZE_WHITESPACE}, \constant{ELLIPSIS},
-    \constant{UNIFIED_DIFF}, \constant{CONTEXT_DIFF}, and
-    \constant{NDIFF_DIFF}
+    \constant{REPORT_UDIFF}, \constant{REPORT_CDIFF}, and
+    \constant{REPORT_NDIFF}
     were added; by default \code{<BLANKLINE>} in expected output
     matches an empty line in actual output; and doctest directives
     were added]{2.4}
diff --git a/Lib/doctest.py b/Lib/doctest.py
index 9a88b7a880b..5e83c184d0e 100644
--- a/Lib/doctest.py
+++ b/Lib/doctest.py
@@ -176,9 +176,9 @@ __all__ = [
     'DONT_ACCEPT_BLANKLINE',
     'NORMALIZE_WHITESPACE',
     'ELLIPSIS',
-    'UNIFIED_DIFF',
-    'CONTEXT_DIFF',
-    'NDIFF_DIFF',
+    'REPORT_UDIFF',
+    'REPORT_CDIFF',
+    'REPORT_NDIFF',
     # 1. Utility Functions
     'is_private',
     # 2. Example & DocTest
@@ -257,9 +257,9 @@ DONT_ACCEPT_TRUE_FOR_1 = register_optionflag('DONT_ACCEPT_TRUE_FOR_1')
 DONT_ACCEPT_BLANKLINE = register_optionflag('DONT_ACCEPT_BLANKLINE')
 NORMALIZE_WHITESPACE = register_optionflag('NORMALIZE_WHITESPACE')
 ELLIPSIS = register_optionflag('ELLIPSIS')
-UNIFIED_DIFF = register_optionflag('UNIFIED_DIFF')
-CONTEXT_DIFF = register_optionflag('CONTEXT_DIFF')
-NDIFF_DIFF = register_optionflag('NDIFF_DIFF')
+REPORT_UDIFF = register_optionflag('REPORT_UDIFF')
+REPORT_CDIFF = register_optionflag('REPORT_CDIFF')
+REPORT_NDIFF = register_optionflag('REPORT_NDIFF')
 
 # Special string markers for use in `want` strings:
 BLANKLINE_MARKER = '<BLANKLINE>'
@@ -1582,9 +1582,9 @@ class OutputChecker:
     # Should we do a fancy diff?
     def _do_a_fancy_diff(self, want, got, optionflags):
         # Not unless they asked for a fancy diff.
-        if not optionflags & (UNIFIED_DIFF |
-                              CONTEXT_DIFF |
-                              NDIFF_DIFF):
+        if not optionflags & (REPORT_UDIFF |
+                              REPORT_CDIFF |
+                              REPORT_NDIFF):
             return False
         # If expected output uses ellipsis, a meaningful fancy diff is
         # too hard.
@@ -1592,7 +1592,7 @@ class OutputChecker:
             return False
         # ndiff does intraline difference marking, so can be useful even
         # for 1-line inputs.
-        if optionflags & NDIFF_DIFF:
+        if optionflags & REPORT_NDIFF:
             return True
         # The other diff types need at least a few lines to be helpful.
         return want.count('\n') > 2 and got.count('\n') > 2
@@ -1617,15 +1617,15 @@ class OutputChecker:
             want_lines = [l+'\n' for l in want.split('\n')]
             got_lines = [l+'\n' for l in got.split('\n')]
             # Use difflib to find their differences.
-            if optionflags & UNIFIED_DIFF:
+            if optionflags & REPORT_UDIFF:
                 diff = difflib.unified_diff(want_lines, got_lines, n=2)
                 diff = list(diff)[2:] # strip the diff header
                 kind = 'unified diff with -expected +actual'
-            elif optionflags & CONTEXT_DIFF:
+            elif optionflags & REPORT_CDIFF:
                 diff = difflib.context_diff(want_lines, got_lines, n=2)
                 diff = list(diff)[2:] # strip the diff header
                 kind = 'context diff with expected followed by actual'
-            elif optionflags & NDIFF_DIFF:
+            elif optionflags & REPORT_NDIFF:
                 engine = difflib.Differ(charjunk=difflib.IS_CHARACTER_JUNK)
                 diff = list(engine.compare(want_lines, got_lines))
                 kind = 'ndiff with -expected +actual'
@@ -1839,9 +1839,9 @@ def testmod(m=None, name=None, globs=None, verbose=None, isprivate=None,
         DONT_ACCEPT_BLANKLINE
         NORMALIZE_WHITESPACE
         ELLIPSIS
-        UNIFIED_DIFF
-        CONTEXT_DIFF
-        NDIFF_DIFF
+        REPORT_UDIFF
+        REPORT_CDIFF
+        REPORT_NDIFF
 
     Optional keyword arg "raise_on_error" raises an exception on the
     first unexpected exception or failure. This allows failures to be
diff --git a/Lib/test/test_doctest.py b/Lib/test/test_doctest.py
index 29c3ec2fe37..d6830510bbf 100644
--- a/Lib/test/test_doctest.py
+++ b/Lib/test/test_doctest.py
@@ -923,7 +923,7 @@ output to match any substring in the actual output:
     ...                 # doctest: +NORMALIZE_WHITESPACE
     [0,    1, ...,   18,    19]
 
-The UNIFIED_DIFF flag causes failures that involve multi-line expected
+The REPORT_UDIFF flag causes failures that involve multi-line expected
 and actual outputs to be displayed using a unified diff:
 
     >>> def f(x):
@@ -965,7 +965,7 @@ and actual outputs to be displayed using a unified diff:
 
     >>> # With the flag:
     >>> test = doctest.DocTestFinder().find(f)[0]
-    >>> flags = doctest.UNIFIED_DIFF
+    >>> flags = doctest.REPORT_UDIFF
     >>> doctest.DocTestRunner(verbose=False, optionflags=flags).run(test)
     **********************************************************************
     Line 2, in f
@@ -985,12 +985,12 @@ and actual outputs to be displayed using a unified diff:
     <BLANKLINE>
     (1, 1)
 
-The CONTEXT_DIFF flag causes failures that involve multi-line expected
+The REPORT_CDIFF flag causes failures that involve multi-line expected
 and actual outputs to be displayed using a context diff:
 
-    >>> # Reuse f() from the UNIFIED_DIFF example, above.
+    >>> # Reuse f() from the REPORT_UDIFF example, above.
     >>> test = doctest.DocTestFinder().find(f)[0]
-    >>> flags = doctest.CONTEXT_DIFF
+    >>> flags = doctest.REPORT_CDIFF
     >>> doctest.DocTestRunner(verbose=False, optionflags=flags).run(test)
     **********************************************************************
     Line 2, in f
@@ -1019,7 +1019,7 @@ and actual outputs to be displayed using a context diff:
     (1, 1)
 
 
-The NDIFF_DIFF flag causes failures to use the difflib.Differ algorithm
+The REPORT_NDIFF flag causes failures to use the difflib.Differ algorithm
 used by the popular ndiff.py utility.  This does intraline difference
 marking, as well as interline differences.
 
@@ -1029,7 +1029,7 @@ marking, as well as interline differences.
     ...     a b c d e f g h i j k 1 m
     ...     '''
     >>> test = doctest.DocTestFinder().find(f)[0]
-    >>> flags = doctest.NDIFF_DIFF
+    >>> flags = doctest.REPORT_NDIFF
     >>> doctest.DocTestRunner(verbose=False, optionflags=flags).run(test)
     **********************************************************************
     Line 2, in f