diff -Naur healpy-1.15.0/healpixsubmodule/src/cxx/cxxsupport/fitshandle.cc healpy-1.15.0.new/healpixsubmodule/src/cxx/cxxsupport/fitshandle.cc
--- healpy-1.15.0/healpixsubmodule/src/cxx/cxxsupport/fitshandle.cc	2021-06-22 13:20:56.000000000 +0200
+++ healpy-1.15.0.new/healpixsubmodule/src/cxx/cxxsupport/fitshandle.cc	2021-12-31 21:44:03.178248445 +0100
@@ -799,12 +799,27 @@
       float fitsversion;
       planck_assert(fits_get_version(&fitsversion),
         "error calling fits_get_version()");
+      /* CFITSIO 4.x switched to a three version format (4.0.0), as opposed
+       * to previous two-number versions (3.47). Version 4 defines a new macro
+       * CFITSIO_MICRO to track the patch level in the version. We check if
+       * macro is defined, and fall back to the old behaviour if it is not.
+       * If it is, we adapt to the new value returned by 'fits_get_version'.
+       */
+#ifdef CFITSIO_MICRO
+      int v_header  = nearest<int>(1E6*CFITSIO_MAJOR + 1000.*CFITSIO_MINOR + CFITSIO_MICRO),
+          v_library = nearest<int>(1E6*fitsversion);
+      if (v_header!=v_library)
+        cerr << endl << "WARNING: version mismatch between CFITSIO header (v"
+             << dataToString(v_header*1.0E-6) << ") and linked library (v"
+             << dataToString(v_library*1.0E-6) << ")." << endl << endl;
+#else
       int v_header  = nearest<int>(1000.*CFITSIO_VERSION),
           v_library = nearest<int>(1000.*fitsversion);
       if (v_header!=v_library)
         cerr << endl << "WARNING: version mismatch between CFITSIO header (v"
              << dataToString(v_header*0.001) << ") and linked library (v"
              << dataToString(v_library*0.001) << ")." << endl << endl;
+#endif
       }
   };