diff --git a/doc/xml/release.xml b/doc/xml/release.xml
index 12091e3d5..653cebede 100644
--- a/doc/xml/release.xml
+++ b/doc/xml/release.xml
@@ -121,6 +121,10 @@
                         <p>Make Valgrind return an error even when a non-fatal issue is detected.  Update some minor issues discovered in the tests as a result.</p>
                     </release-item>
 
+                    <release-item>
+                        <p>Add <id>-ftree-coalesce-vars</id> option to unit test compilation.</p>
+                    </release-item>
+
                     <release-item>
                         <p>Clear test directory between test runs.</p>
                     </release-item>
diff --git a/test/lib/pgBackRestTest/Common/JobTest.pm b/test/lib/pgBackRestTest/Common/JobTest.pm
index 302bcd8c8..80e897fdb 100644
--- a/test/lib/pgBackRestTest/Common/JobTest.pm
+++ b/test/lib/pgBackRestTest/Common/JobTest.pm
@@ -400,6 +400,7 @@ sub run
                     "\n" .
                     "test.o: test.c\n" .
 	                "\t\$(CC) \$(CFLAGS) \$(TESTFLAGS) -O0" .
+                        ($self->{oTest}->{&TEST_VM} ne VM_U12 ? ' -ftree-coalesce-vars' : '') .
                         (vmCoverageC($self->{oTest}->{&TEST_VM}) && $self->{bCoverageUnit} ?
                             ' -fprofile-arcs -ftest-coverage' : '') .
                         " -c test.c\n" .