diff --git a/cmake/MusrfitCheckROOT7.cmake b/cmake/MusrfitCheckROOT7.cmake
index 620ec5ae..52111a69 100644
--- a/cmake/MusrfitCheckROOT7.cmake
+++ b/cmake/MusrfitCheckROOT7.cmake
@@ -138,6 +138,15 @@ set(CMAKE_REQUIRED_QUIET TRUE)
 set(_musrview_try_compile_type_save "${CMAKE_TRY_COMPILE_TARGET_TYPE}")
 set(CMAKE_TRY_COMPILE_TARGET_TYPE STATIC_LIBRARY)
 
+#--- check_cxx_source_compiles() caches its result under a plain variable
+#--- name with no dependency tracking: if it once failed (e.g. against an
+#--- older ROOT in this same build directory) it would keep reporting that
+#--- stale failure on every later reconfigure, even after ROOT got fixed,
+#--- since neither the test source nor ROOT_VERSION are part of the cache
+#--- key. Unset both results first so the compile check always re-runs. ------
+unset(MUSRVIEW_HAS_ROOT7_API CACHE)
+unset(MUSRVIEW_HAS_ROOT7_API_EXPERIMENTAL CACHE)
+
 set(MUSRVIEW_NS "ROOT::")
 string(CONFIGURE "${MUSRVIEW_ROOT7_API_TEST_SRC}" _musrview_api_src @ONLY)
 check_cxx_source_compiles("${_musrview_api_src}" MUSRVIEW_HAS_ROOT7_API)