diff --git a/libavcodec/utils.c b/libavcodec/utils.c
index 0397d3b68d..102a0490b0 100644
--- a/libavcodec/utils.c
+++ b/libavcodec/utils.c
@@ -206,7 +206,8 @@ av_cold void avcodec_register(AVCodec *codec)
     avcodec_init();
     p = &first_avcodec;
     codec->next = NULL;
-    while(avpriv_atomic_ptr_cas((void * volatile *)p, NULL, codec))
+
+    while(*p || avpriv_atomic_ptr_cas((void * volatile *)p, NULL, codec))
         p = &(*p)->next;
 
     if (codec->init_static_data)
@@ -3191,7 +3192,7 @@ void av_register_hwaccel(AVHWAccel *hwaccel)
 {
     AVHWAccel **p = &first_hwaccel;
     hwaccel->next = NULL;
-    while(avpriv_atomic_ptr_cas((void * volatile *)p, NULL, hwaccel))
+    while(*p || avpriv_atomic_ptr_cas((void * volatile *)p, NULL, hwaccel))
         p = &(*p)->next;
 }
 
diff --git a/libavfilter/avfilter.c b/libavfilter/avfilter.c
index 14ce55f932..2567ce92c1 100644
--- a/libavfilter/avfilter.c
+++ b/libavfilter/avfilter.c
@@ -490,7 +490,7 @@ int avfilter_register(AVFilter *filter)
 
     filter->next = NULL;
 
-    while(avpriv_atomic_ptr_cas((void * volatile *)f, NULL, filter))
+    while(*f || avpriv_atomic_ptr_cas((void * volatile *)f, NULL, filter))
         f = &(*f)->next;
 
     return 0;
diff --git a/libavformat/format.c b/libavformat/format.c
index ac9100b604..36c0131c12 100644
--- a/libavformat/format.c
+++ b/libavformat/format.c
@@ -54,7 +54,7 @@ void av_register_input_format(AVInputFormat *format)
     AVInputFormat **p = &first_iformat;
 
     format->next = NULL;
-    while(avpriv_atomic_ptr_cas((void * volatile *)p, NULL, format))
+    while(*p || avpriv_atomic_ptr_cas((void * volatile *)p, NULL, format))
         p = &(*p)->next;
 }
 
@@ -63,7 +63,7 @@ void av_register_output_format(AVOutputFormat *format)
     AVOutputFormat **p = &first_oformat;
 
     format->next = NULL;
-    while(avpriv_atomic_ptr_cas((void * volatile *)p, NULL, format))
+    while(*p || avpriv_atomic_ptr_cas((void * volatile *)p, NULL, format))
         p = &(*p)->next;
 }