diff --git a/src/gswe-antiscion-data.c b/src/gswe-antiscion-data.c
index c46c47f..7e74c91 100644
--- a/src/gswe-antiscion-data.c
+++ b/src/gswe-antiscion-data.c
@@ -220,6 +220,10 @@ gswe_antiscion_data_ref(GsweAntiscionData *antiscion_data)
 void
 gswe_antiscion_data_unref(GsweAntiscionData *antiscion_data)
 {
+    if (antiscion_data == NULL) {
+        return;
+    }
+
     if (--antiscion_data->refcount == 0) {
         gswe_antiscion_data_free(antiscion_data);
     }
diff --git a/src/gswe-aspect-data.c b/src/gswe-aspect-data.c
index a6fc6f2..a2ebc6c 100644
--- a/src/gswe-aspect-data.c
+++ b/src/gswe-aspect-data.c
@@ -203,6 +203,10 @@ gswe_aspect_data_ref(GsweAspectData *aspect_data)
 void
 gswe_aspect_data_unref(GsweAspectData *aspect_data)
 {
+    if (aspect_data == NULL) {
+        return;
+    }
+
     if (--aspect_data->refcount == 0) {
         gswe_aspect_data_free(aspect_data);
     }
diff --git a/src/gswe-moon-phase-data.c b/src/gswe-moon-phase-data.c
index bc3976a..edc361c 100644
--- a/src/gswe-moon-phase-data.c
+++ b/src/gswe-moon-phase-data.c
@@ -88,6 +88,10 @@ gswe_moon_phase_data_ref(GsweMoonPhaseData *moon_phase_data)
 void
 gswe_moon_phase_data_unref(GsweMoonPhaseData *moon_phase_data)
 {
+    if (moon_phase_data == NULL) {
+        return;
+    }
+
     if (--moon_phase_data->refcount == 0) {
         g_free(moon_phase_data);
     }
diff --git a/src/gswe-planet-data.c b/src/gswe-planet-data.c
index 11c47ed..98a25de 100644
--- a/src/gswe-planet-data.c
+++ b/src/gswe-planet-data.c
@@ -99,6 +99,10 @@ gswe_planet_data_ref(GswePlanetData *planet_data)
 void
 gswe_planet_data_unref(GswePlanetData *planet_data)
 {
+    if (planet_data == NULL) {
+        return;
+    }
+
     if (--planet_data->refcount == 0) {
         gswe_planet_data_free(planet_data);
     }