diff --git a/libs/ardour/audiosource.cc b/libs/ardour/audiosource.cc
index aea0203394..559a9c616d 100644
--- a/libs/ardour/audiosource.cc
+++ b/libs/ardour/audiosource.cc
@@ -926,7 +926,9 @@ AudioSource::compute_and_write_peaks (Sample* buf, samplecnt_t first_sample, sam
 		memcpy (buf2.get(), peak_leftovers, peak_leftover_cnt * sizeof (Sample));
 
 		/* the new stuff */
-		memcpy (buf2.get()+peak_leftover_cnt, buf, cnt * sizeof (Sample));
+		if (buf && cnt > 0) {
+			memcpy (buf2.get()+peak_leftover_cnt, buf, cnt * sizeof (Sample));
+		}
 
 		/* no more leftovers */
 		peak_leftover_cnt = 0;
diff --git a/libs/backends/alsa/alsa_midi.cc b/libs/backends/alsa/alsa_midi.cc
index d9d473a84d..8bf7f4aece 100644
--- a/libs/backends/alsa/alsa_midi.cc
+++ b/libs/backends/alsa/alsa_midi.cc
@@ -186,7 +186,7 @@ AlsaMidiIn::recv_event (pframes_t &time, uint8_t *data, size_t &size)
 		if (vector.len[0] > 0) {
 			memcpy ((uint8_t*)&h, vector.buf[0], vector.len[0]);
 		}
-		assert(vector.buf[1] || vector.len[0] == sizeof(MidiEventHeader));
+		assert(vector.buf[1]);
 		memcpy (((uint8_t*)&h) + vector.len[0], vector.buf[1], sizeof(MidiEventHeader) - vector.len[0]);
 	}
 
diff --git a/libs/evoral/src/SMF.cpp b/libs/evoral/src/SMF.cpp
index b5d34aa538..60d69c8a4d 100644
--- a/libs/evoral/src/SMF.cpp
+++ b/libs/evoral/src/SMF.cpp
@@ -326,6 +326,7 @@ SMF::read_event(uint32_t* delta_t, uint32_t* size, uint8_t** buf, event_id_t* no
 		if (*size < (unsigned)event_size) {
 			*buf = (uint8_t*)realloc(*buf, event_size);
 		}
+		assert (*buf);
 		memcpy(*buf, event->midi_buffer, size_t(event_size));
 		*size = event_size;
 		if (((*buf)[0] & 0xF0) == 0x90 && (*buf)[2] == 0) {