diff --git a/expat/CMakeLists.txt b/expat/CMakeLists.txt
index dd793188..6649d769 100644
--- a/expat/CMakeLists.txt
+++ b/expat/CMakeLists.txt
@@ -676,6 +676,8 @@ if(EXPAT_BUILD_TESTS)
     )
 
     foreach(_target ${_EXPAT_TEST_TARGETS})
+        target_compile_definitions(${_target} PRIVATE -DXML_TESTING)
+
         set_property(TARGET ${_target} PROPERTY RUNTIME_OUTPUT_DIRECTORY tests)
         expat_add_test(${_target} $<TARGET_FILE:${_target}>)
 
diff --git a/expat/apply-clang-tidy.sh b/expat/apply-clang-tidy.sh
index 2e520bd0..17015f6c 100755
--- a/expat/apply-clang-tidy.sh
+++ b/expat/apply-clang-tidy.sh
@@ -68,6 +68,7 @@ flags=(
     -DXML_DTD
     -DXML_GE
     -DXML_NS
+    -DXML_TESTING
 )
 
 if [[ $# -gt 0 ]]; then
diff --git a/expat/lib/Makefile.am b/expat/lib/Makefile.am
index 1ecb8fa2..f32430ab 100644
--- a/expat/lib/Makefile.am
+++ b/expat/lib/Makefile.am
@@ -52,6 +52,8 @@ libexpat_la_SOURCES = \
     xmlrole.c
 
 if WITH_TESTS
+libtestpat_la_CPPFLAGS = -DXML_TESTING
+
 libtestpat_la_SOURCES = $(libexpat_la_SOURCES)
 endif
 
diff --git a/expat/lib/internal.h b/expat/lib/internal.h
index cdbd3609..81db8955 100644
--- a/expat/lib/internal.h
+++ b/expat/lib/internal.h
@@ -161,8 +161,14 @@ unsigned long long testingAccountingGetCountBytesIndirect(XML_Parser parser);
 const char *unsignedCharToPrintable(unsigned char c);
 #endif
 
-extern XML_Bool g_reparseDeferralEnabledDefault; // written ONLY in runtests.c
-extern unsigned int g_bytesScanned;              // used for testing only
+extern
+#if ! defined(XML_TESTING)
+    const
+#endif
+    XML_Bool g_reparseDeferralEnabledDefault; // written ONLY in runtests.c
+#if defined(XML_TESTING)
+extern unsigned int g_bytesScanned; // used for testing only
+#endif
 
 #ifdef __cplusplus
 }
diff --git a/expat/lib/xmlparse.c b/expat/lib/xmlparse.c
index 63fcaa92..0451e693 100644
--- a/expat/lib/xmlparse.c
+++ b/expat/lib/xmlparse.c
@@ -629,8 +629,14 @@ static unsigned long getDebugLevel(const char *variableName,
        ? 0                                                                     \
        : ((*((pool)->ptr)++ = c), 1))
 
-XML_Bool g_reparseDeferralEnabledDefault = XML_TRUE; // write ONLY in runtests.c
-unsigned int g_bytesScanned = 0;                     // used for testing only
+#if ! defined(XML_TESTING)
+const
+#endif
+    XML_Bool g_reparseDeferralEnabledDefault
+    = XML_TRUE; // write ONLY in runtests.c
+#if defined(XML_TESTING)
+unsigned int g_bytesScanned = 0; // used for testing only
+#endif
 
 struct XML_ParserStruct {
   /* The first member must be m_userData so that the XML_GetUserData
@@ -1017,7 +1023,9 @@ callProcessor(XML_Parser parser, const char *start, const char *end,
       return XML_ERROR_NONE;
     }
   }
+#if defined(XML_TESTING)
   g_bytesScanned += (unsigned)have_now;
+#endif
   const enum XML_Error ret = parser->m_processor(parser, start, end, endPtr);
   if (ret == XML_ERROR_NONE) {
     // if we consumed nothing, remember what we had on this parse attempt.
diff --git a/expat/tests/Makefile.am b/expat/tests/Makefile.am
index 97da3bf6..e1ab9f8c 100644
--- a/expat/tests/Makefile.am
+++ b/expat/tests/Makefile.am
@@ -32,7 +32,7 @@
 
 SUBDIRS = . benchmark
 
-AM_CPPFLAGS = @AM_CPPFLAGS@ -I$(srcdir)/../lib
+AM_CPPFLAGS = @AM_CPPFLAGS@ -I$(srcdir)/../lib -DXML_TESTING
 
 check_PROGRAMS = runtests runtests_cxx
 TESTS = runtests runtests_cxx