diff --git a/tests/src/unit-custom-array-type.cpp b/tests/src/unit-custom-array-type.cpp
index be25469b0..f10455f15 100644
--- a/tests/src/unit-custom-array-type.cpp
+++ b/tests/src/unit-custom-array-type.cpp
@@ -19,8 +19,9 @@
 
 // TEMPORARY: this translation unit is disabled to narrow down an AppVeyor
 // failure on MSVC 2015/2017 whose build log this environment cannot reach.
-// The guard is removed again as soon as the cause is known.
-#if 0
+// The macro is deliberately never defined; the guard is removed again as soon
+// as the cause is known.
+#ifdef JSON_BISECT_CUSTOM_CONTAINER_TESTS
 
 namespace
 {
diff --git a/tests/src/unit-custom-binary-type.cpp b/tests/src/unit-custom-binary-type.cpp
index e7191b296..b7718a769 100644
--- a/tests/src/unit-custom-binary-type.cpp
+++ b/tests/src/unit-custom-binary-type.cpp
@@ -23,8 +23,9 @@
 
 // TEMPORARY: this translation unit is disabled to narrow down an AppVeyor
 // failure on MSVC 2015/2017 whose build log this environment cannot reach.
-// The guard is removed again as soon as the cause is known.
-#if 0
+// The macro is deliberately never defined; the guard is removed again as soon
+// as the cause is known.
+#ifdef JSON_BISECT_CUSTOM_CONTAINER_TESTS
 
 namespace
 {
diff --git a/tests/src/unit-custom-object-type.cpp b/tests/src/unit-custom-object-type.cpp
index 5bf12797f..ef1abface 100644
--- a/tests/src/unit-custom-object-type.cpp
+++ b/tests/src/unit-custom-object-type.cpp
@@ -19,8 +19,9 @@
 
 // TEMPORARY: this translation unit is disabled to narrow down an AppVeyor
 // failure on MSVC 2015/2017 whose build log this environment cannot reach.
-// The guard is removed again as soon as the cause is known.
-#if 0
+// The macro is deliberately never defined; the guard is removed again as soon
+// as the cause is known.
+#ifdef JSON_BISECT_CUSTOM_CONTAINER_TESTS
 
 namespace
 {