diff --git a/tests/coverage.h b/tests/coverage.h
index 9ef57a47..6e6b9c3f 100644
--- a/tests/coverage.h
+++ b/tests/coverage.h
@@ -149,6 +149,7 @@
 #undef M_ASSIGN_CAST
 #undef M_CHECK_DEFAULT_TYPE
 #undef M_CHECK_SAME
+#undef isspace
 #else
 /* For normal builds, empty macros which does nothing */
 #define START_COVERAGE