diff --git a/lib/fits.c b/lib/fits.c
index ef559759..5fe11bd6 100644
--- a/lib/fits.c
+++ b/lib/fits.c
@@ -2138,8 +2138,19 @@ gal_fits_key_write_version_in_ptr(gal_fits_list_key_t **keylist, char *title,
   /* Print 'Versions and date' title. */
   gal_fits_key_write_title_in_ptr("Versions and date", fptr);
 
-  /* Set the version of CFITSIO as a string. */
-  sprintf(cfitsioversion, "%-.2f", CFITSIO_VERSION);
+  /* Set the version of CFITSIO as a string: before version 4.0.0 of
+     CFITSIO, there were only two numbers in the version (for example
+     '3.49' and '3.48'), but from the 4th major release, there are three
+     numbers in the version string. The third number corresponds to a new
+     'CFITSIO_MICRO' macro. So if it doesn't exist, we'll just print two
+     numbers, otherwise, we'll print the three. */
+#ifdef CFITSIO_MICRO
+  sprintf(cfitsioversion, "%d.%d.%d", CFITSIO_MAJOR,
+          CFITSIO_MINOR, CFITSIO_MICRO);
+#else
+  sprintf(cfitsioversion, "%d.%d", CFITSIO_MAJOR,
+          CFITSIO_MINOR);
+#endif
 
   /* Write all the information: */
   fits_write_date(fptr, &status);