diff --git a/CHANGELOG.md b/CHANGELOG.md
index 1acb345a..24f9de39 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -12,6 +12,13 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.1.0/),
 Release candidate for the next feature release, expected around 1 February 2025.
 
 
+### Fixed
+
+ - `make_on_surface()` to leave humidity undefined. The `humidity` field was added in v1.1 only, and thus attempting
+   to initialize it to zero can use memory corruption or even segfaulting if called by objects that have been compiled
+   with v1.0. So, from now on the call will leave humidity uninitialized and it's up to the calle ro define it if it
+   is needed for the specific refraction model.
+
 ### Added
 
  - #57: New `novas_make_redshifted_object()` to simplify the creation of distant catalog sources that are 
diff --git a/include/novas.h b/include/novas.h
index 4a85b5d1..d1fd7dbe 100644
--- a/include/novas.h
+++ b/include/novas.h
@@ -807,14 +807,12 @@ typedef struct {
 } object;
 
 /**
- * data for an observer's location on the surface of
- * the Earth.  The atmospheric parameters are used
- * only by the refraction function called from
- * function 'equ2hor'. Additional parameters can be
- * added to this structure if a more sophisticated
- * refraction model is employed.
+ * Data for an observer's location on the surface of the Earth, and optional local weather data for
+ * refraction calculations only.
  *
  * @sa observer
+ * @sa make_on_surface()
+ * @sa ON_SURFACE_INIT
  */
 typedef struct {
   double latitude;      ///< [deg] geodetic (ITRS) latitude; north positive
@@ -825,11 +823,20 @@ typedef struct {
   double humidity;      ///< [%] Relative humidity. @since 1.1
 } on_surface;
 
+/**
+ * Initialized for a NOVAS on_surface data structure.
+ *
+ * @sa on_surface
+ * @since 1.2
+ */
+#define ON_SURFACE_INIT { 0.0, 0.0, 0.0, 0.0, 0.0, 0.0 }
+
 /**
  * data for an observer's location on Earth orbit
  *
  * @sa observer
  * @sa IN_SPACE_INIT
+ * @sa make_in_space()
  */
 typedef struct {
   double sc_pos[3];     ///< [km] geocentric (or [AU] ICRS barycentric) position vector (x, y, z)
@@ -846,6 +853,11 @@ typedef struct {
 /**
  * Observer location.
  *
+ * @sa make_observer()
+ * @sa make_observer_at_geocenter()
+ * @sa make_observer_on_earth()
+ * @sa make_observer_in_space()
+ * @sa make_solar_system_observer()
  */
 typedef struct {
   enum novas_observer_place where;    ///< observer location type
@@ -860,6 +872,7 @@ typedef struct {
   in_space near_earth;
 } observer;
 
+
 /**
  * Celestial object's place on the sky; contains the output from place()
  *
diff --git a/src/novas.c b/src/novas.c
index 587e36b8..7252bc65 100644
--- a/src/novas.c
+++ b/src/novas.c
@@ -6840,6 +6840,7 @@ int make_planet(enum novas_planet num, object *planet) {
  * @sa make_observer_at_geocenter()
  * @sa make_observer_on_surface()
  * @sa make_observer_in_space()
+ * @sa make_solar_system_observer()
  */
 short make_observer(enum novas_observer_place where, const on_surface *loc_surface, const in_space *loc_space, observer *obs) {
   static const char *fn = "make_observer";
@@ -6956,9 +6957,9 @@ int make_observer_in_space(const double *sc_pos, const double *sc_vel, observer
  * the given parameters.
  *
  * Note, that because this is an original NOVAS C routine, it does not have an argument to set
- * a humidity value (e.g. for radio refraction). As such the call will set humidity to 0.0.
- * To set the humidity, set the output structure's field after calling this funcion. Its unit
- * is [%], and so the range is 0.0--100.0.
+ * a humidity value (e.g. for radio refraction). As such, the humidity value remains undefined
+ * after this call. To set the humidity, set the output structure's field after calling this
+ * funcion. Its unit is [%], and so the range is 0.0--100.0.
  *
  * @param latitude      [deg] Geodetic (ITRS) latitude in degrees; north positive.
  * @param longitude     [deg] Geodetic (ITRS) longitude in degrees; east positive.
@@ -6981,7 +6982,9 @@ int make_on_surface(double latitude, double longitude, double height, double tem
   loc->height = height;
   loc->temperature = temperature;
   loc->pressure = pressure;
-  loc->humidity = 0.0;
+
+  // FIXME starting v2.0 set humidity to 0.0
+  //loc->humidity = 0.0;
 
   return 0;
 }
diff --git a/src/refract.c b/src/refract.c
index 11a71e61..3b40cc16 100644
--- a/src/refract.c
+++ b/src/refract.c
@@ -176,6 +176,12 @@ double novas_radio_refraction(double jd_tt, const on_surface *loc, enum novas_re
     return NAN;
   }
 
+
+  if(loc->humidity < -1.0 || loc->humidity > 101.0) {
+    novas_set_errno(EINVAL, fn, "invalid humidity value: %g", loc->humidity);
+    return NAN;
+  }
+
   if(type == NOVAS_REFRACT_OBSERVED)
     return novas_inv_refract(novas_radio_refraction, jd_tt, loc, NOVAS_REFRACT_ASTROMETRIC, el);
 
diff --git a/test/src/test-errors.c b/test/src/test-errors.c
index 98815fca..1f21dfa5 100644
--- a/test/src/test-errors.c
+++ b/test/src/test-errors.c
@@ -1149,6 +1149,12 @@ static int test_refraction() {
   novas_optical_refraction(NOVAS_JD_J2000, NULL, NOVAS_REFRACT_OBSERVED, 10.0);
   novas_debug(0);
 
+  obs.humidity = -1.01;
+  if(check_nan("radio_refraction:humidity:lo", novas_radio_refraction(NOVAS_JD_J2000, &obs, NOVAS_REFRACT_OBSERVED, 10.0))) n++;
+
+  obs.humidity = 101.01;
+  if(check_nan("radio_refraction:humidity:hi", novas_radio_refraction(NOVAS_JD_J2000, &obs, NOVAS_REFRACT_OBSERVED, 10.0))) n++;
+
   return n;
 }