diff --git a/gobject/gboxed.c b/gobject/gboxed.c
index 87cc5d2c2..a4c2c3805 100644
--- a/gobject/gboxed.c
+++ b/gobject/gboxed.c
@@ -256,8 +256,7 @@ boxed_proxy_lcopy_value (const GValue *value,
 {
   gpointer *boxed_p = collect_values[0].v_pointer;
 
-  if (!boxed_p)
-    return g_strdup_printf ("value location for '%s' passed as NULL", G_VALUE_TYPE_NAME (value));
+  g_return_val_if_fail (boxed_p != NULL, g_strdup_printf ("value location for '%s' passed as NULL", G_VALUE_TYPE_NAME (value)));
 
   if (!value->data[0].v_pointer)
     *boxed_p = NULL;
diff --git a/gobject/genums.c b/gobject/genums.c
index f78370053..7fb2521a2 100644
--- a/gobject/genums.c
+++ b/gobject/genums.c
@@ -167,10 +167,9 @@ value_flags_enum_lcopy_value (const GValue *value,
 			      guint         collect_flags)
 {
   gint *int_p = collect_values[0].v_pointer;
-  
-  if (!int_p)
-    return g_strdup_printf ("value location for '%s' passed as NULL", G_VALUE_TYPE_NAME (value));
-  
+
+  g_return_val_if_fail (int_p != NULL, g_strdup_printf ("value location for '%s' passed as NULL", G_VALUE_TYPE_NAME (value)));
+
   *int_p = value->data[0].v_long;
   
   return NULL;
diff --git a/gobject/gobject.c b/gobject/gobject.c
index c5b3b83a8..5c4aa60a6 100644
--- a/gobject/gobject.c
+++ b/gobject/gobject.c
@@ -4021,9 +4021,8 @@ g_value_object_lcopy_value (const GValue *value,
 			    guint        collect_flags)
 {
   GObject **object_p = collect_values[0].v_pointer;
-  
-  if (!object_p)
-    return g_strdup_printf ("value location for '%s' passed as NULL", G_VALUE_TYPE_NAME (value));
+
+  g_return_val_if_fail (object_p != NULL, g_strdup_printf ("value location for '%s' passed as NULL", G_VALUE_TYPE_NAME (value)));
 
   if (!value->data[0].v_pointer)
     *object_p = NULL;
diff --git a/gobject/gparam.c b/gobject/gparam.c
index 5fd895312..2cd4c692c 100644
--- a/gobject/gparam.c
+++ b/gobject/gparam.c
@@ -871,8 +871,7 @@ value_param_lcopy_value (const GValue *value,
 {
   GParamSpec **param_p = collect_values[0].v_pointer;
 
-  if (!param_p)
-    return g_strdup_printf ("value location for '%s' passed as NULL", G_VALUE_TYPE_NAME (value));
+  g_return_val_if_fail (param_p != NULL, g_strdup_printf ("value location for '%s' passed as NULL", G_VALUE_TYPE_NAME (value)));
 
   if (!value->data[0].v_pointer)
     *param_p = NULL;
diff --git a/gobject/gtype.h b/gobject/gtype.h
index 479b405e9..89178411f 100644
--- a/gobject/gtype.h
+++ b/gobject/gtype.h
@@ -1178,17 +1178,13 @@ struct _GInterfaceInfo
  *  array.  To deviate from our string example for a moment, and taking
  *  a look at an exemplary implementation for collect_value() of
  *  #GObject:
- *  |[<!-- language="C" -->
- *  if (collect_values[0].v_pointer)
- *  {
+ *  |[<!-- language="C" --> 
  *    GObject *object = G_OBJECT (collect_values[0].v_pointer);
+ *    g_return_val_if_fail (object != NULL,
+ *       g_strdup_printf ("Object passed as invalid NULL pointer"));
  *    // never honour G_VALUE_NOCOPY_CONTENTS for ref-counted types
  *    value->data[0].v_pointer = g_object_ref (object);
  *    return NULL;
- *  }
- *  else
- *    return g_strdup_printf ("Object passed as invalid NULL pointer");
- *  }
  *  ]|
  *  The reference count for valid objects is always incremented,
  *  regardless of @collect_flags. For invalid objects, the example
@@ -1220,8 +1216,8 @@ struct _GInterfaceInfo
  *  To complete the string example:
  *  |[<!-- language="C" -->
  *  gchar **string_p = collect_values[0].v_pointer;
- *  if (!string_p)
- *    return g_strdup_printf ("string location passed as NULL");
+ *  g_return_val_if_fail (string_p != NULL,
+ *      g_strdup_printf ("string location passed as NULL"));
  *  if (collect_flags & G_VALUE_NOCOPY_CONTENTS)
  *    *string_p = value->data[0].v_pointer;
  *  else
@@ -1231,8 +1227,8 @@ struct _GInterfaceInfo
  *  reference-counted types:
  *  |[<!-- language="C" -->
  *  GObject **object_p = collect_values[0].v_pointer;
- *  if (!object_p)
- *    return g_strdup_printf ("object location passed as NULL");
+ *  g_return_val_if_fail (object_p != NULL,
+ *    g_strdup_printf ("object location passed as NULL"));
  *  if (!value->data[0].v_pointer)
  *    *object_p = NULL;
  *  else if (collect_flags & G_VALUE_NOCOPY_CONTENTS) // always honour
diff --git a/gobject/gvaluetypes.c b/gobject/gvaluetypes.c
index 8052c315e..9eaba43ce 100644
--- a/gobject/gvaluetypes.c
+++ b/gobject/gvaluetypes.c
@@ -55,10 +55,9 @@ value_lcopy_char (const GValue *value,
 		  guint         collect_flags)
 {
   gint8 *int8_p = collect_values[0].v_pointer;
-  
-  if (!int8_p)
-    return g_strdup_printf ("value location for '%s' passed as NULL", G_VALUE_TYPE_NAME (value));
-  
+
+  g_return_val_if_fail (int8_p != NULL, g_strdup_printf ("value location for '%s' passed as NULL", G_VALUE_TYPE_NAME (value)));
+
   *int8_p = value->data[0].v_int;
   
   return NULL;
@@ -71,10 +70,9 @@ value_lcopy_boolean (const GValue *value,
 		     guint         collect_flags)
 {
   gboolean *bool_p = collect_values[0].v_pointer;
-  
-  if (!bool_p)
-    return g_strdup_printf ("value location for '%s' passed as NULL", G_VALUE_TYPE_NAME (value));
-  
+
+  g_return_val_if_fail (bool_p != NULL, g_strdup_printf ("value location for '%s' passed as NULL", G_VALUE_TYPE_NAME (value)));
+
   *bool_p = value->data[0].v_int;
   
   return NULL;
@@ -98,10 +96,9 @@ value_lcopy_int (const GValue *value,
 		 guint         collect_flags)
 {
   gint *int_p = collect_values[0].v_pointer;
-  
-  if (!int_p)
-    return g_strdup_printf ("value location for '%s' passed as NULL", G_VALUE_TYPE_NAME (value));
-  
+
+  g_return_val_if_fail (int_p != NULL, g_strdup_printf ("value location for '%s' passed as NULL", G_VALUE_TYPE_NAME (value)));
+
   *int_p = value->data[0].v_int;
   
   return NULL;
@@ -125,10 +122,9 @@ value_lcopy_long (const GValue *value,
 		  guint         collect_flags)
 {
   glong *long_p = collect_values[0].v_pointer;
-  
-  if (!long_p)
-    return g_strdup_printf ("value location for '%s' passed as NULL", G_VALUE_TYPE_NAME (value));
-  
+
+  g_return_val_if_fail (long_p != NULL, g_strdup_printf ("value location for '%s' passed as NULL", G_VALUE_TYPE_NAME (value)));
+
   *long_p = value->data[0].v_long;
   
   return NULL;
@@ -165,10 +161,9 @@ value_lcopy_int64 (const GValue *value,
 		   guint         collect_flags)
 {
   gint64 *int64_p = collect_values[0].v_pointer;
-  
-  if (!int64_p)
-    return g_strdup_printf ("value location for '%s' passed as NULL", G_VALUE_TYPE_NAME (value));
-  
+
+  g_return_val_if_fail (int64_p != NULL, g_strdup_printf ("value location for '%s' passed as NULL", G_VALUE_TYPE_NAME (value)));
+
   *int64_p = value->data[0].v_int64;
   
   return NULL;
@@ -205,10 +200,9 @@ value_lcopy_float (const GValue *value,
 		   guint         collect_flags)
 {
   gfloat *float_p = collect_values[0].v_pointer;
-  
-  if (!float_p)
-    return g_strdup_printf ("value location for '%s' passed as NULL", G_VALUE_TYPE_NAME (value));
-  
+
+  g_return_val_if_fail (float_p != NULL, g_strdup_printf ("value location for '%s' passed as NULL", G_VALUE_TYPE_NAME (value)));
+
   *float_p = value->data[0].v_float;
   
   return NULL;
@@ -245,10 +239,9 @@ value_lcopy_double (const GValue *value,
 		    guint         collect_flags)
 {
   gdouble *double_p = collect_values[0].v_pointer;
-  
-  if (!double_p)
-    return g_strdup_printf ("value location for '%s' passed as NULL", G_VALUE_TYPE_NAME (value));
-  
+
+  g_return_val_if_fail (double_p != NULL, g_strdup_printf ("value location for '%s' passed as NULL", G_VALUE_TYPE_NAME (value)));
+
   *double_p = value->data[0].v_double;
   
   return NULL;
@@ -309,10 +302,9 @@ value_lcopy_string (const GValue *value,
 		    guint         collect_flags)
 {
   gchar **string_p = collect_values[0].v_pointer;
-  
-  if (!string_p)
-    return g_strdup_printf ("value location for '%s' passed as NULL", G_VALUE_TYPE_NAME (value));
-  
+
+  g_return_val_if_fail (string_p != NULL, g_strdup_printf ("value location for '%s' passed as NULL", G_VALUE_TYPE_NAME (value)));
+
   if (!value->data[0].v_pointer)
     *string_p = NULL;
   else if (collect_flags & G_VALUE_NOCOPY_CONTENTS)
@@ -361,8 +353,7 @@ value_lcopy_pointer (const GValue *value,
 {
   gpointer *pointer_p = collect_values[0].v_pointer;
 
-  if (!pointer_p)
-    return g_strdup_printf ("value location for '%s' passed as NULL", G_VALUE_TYPE_NAME (value));
+  g_return_val_if_fail (pointer_p != NULL, g_strdup_printf ("value location for '%s' passed as NULL", G_VALUE_TYPE_NAME (value)));
 
   *pointer_p = value->data[0].v_pointer;
 
@@ -414,8 +405,7 @@ value_lcopy_variant (const GValue *value,
 {
   GVariant **variant_p = collect_values[0].v_pointer;
 
-  if (!variant_p)
-    return g_strdup_printf ("value location for '%s' passed as NULL", G_VALUE_TYPE_NAME (value));
+  g_return_val_if_fail (variant_p != NULL, g_strdup_printf ("value location for '%s' passed as NULL", G_VALUE_TYPE_NAME (value)));
 
   if (!value->data[0].v_pointer)
     *variant_p = NULL;