diff --git a/src/audio/capture/testcard.c b/src/audio/capture/testcard.c
index 7215d6ca4..4010af743 100644
--- a/src/audio/capture/testcard.c
+++ b/src/audio/capture/testcard.c
@@ -277,6 +277,7 @@ static void * audio_cap_testcard_init(struct module *parent, const char *cfg)
                                 s->chunk_size = atoi(item + strlen("frames="));
                         } else if (strncasecmp(item, "frequency=", strlen("frequency=")) == 0) {
                                 frequency = atoi(item + strlen("frequency="));
+                                assert(frequency != 0);
                         } else if(strstr(item, "crescendo") == item) {
                                 pattern = CRESCENDO;
                                 char *val = strchr(item, '=');
diff --git a/src/utils/color_out.h b/src/utils/color_out.h
index 5c2eea751..057b43e70 100644
--- a/src/utils/color_out.h
+++ b/src/utils/color_out.h
@@ -109,7 +109,7 @@ class col
 {
 public:
         template<class T>
-        col &operator<< (T val) {
+        col &operator<< (const T& val) {
                 oss << val;
                 return *this;
         }
diff --git a/src/video_capture/import.c b/src/video_capture/import.c
index 32ec53752..eeeaa7255 100644
--- a/src/video_capture/import.c
+++ b/src/video_capture/import.c
@@ -1099,6 +1099,7 @@ vidcap_import_grab(void *state, struct audio_frame **audio)
                 }
  
                 if(s->queue_len == 0) {
+                        pthread_mutex_unlock(&s->lock);
                         return NULL;
                 }