diff --git a/include/jemalloc/internal/buf_writer.h b/include/jemalloc/internal/buf_writer.h
index 1acda9a4..60bd0108 100644
--- a/include/jemalloc/internal/buf_writer.h
+++ b/include/jemalloc/internal/buf_writer.h
@@ -23,7 +23,9 @@ buf_write_init(buf_write_arg_t *arg, void (*write_cb)(void *, const char *),
     void *cbopaque, char *buf, size_t buf_len) {
 	arg->write_cb = write_cb;
 	arg->cbopaque = cbopaque;
+	assert(buf != NULL);
 	arg->buf = buf;
+	assert(buf_len >= 2);
 	arg->buf_size = buf_len - 1; /* Accommodating '\0' at the end. */
 	arg->buf_end = 0;
 }
diff --git a/src/jemalloc.c b/src/jemalloc.c
index 64550613..218e04a1 100644
--- a/src/jemalloc.c
+++ b/src/jemalloc.c
@@ -3716,12 +3716,16 @@ je_malloc_stats_print(void (*write_cb)(void *, const char *), void *cbopaque,
 		char *buf = (char *)iallocztm(tsdn, STATS_PRINT_BUFSIZE,
 		    sz_size2index(STATS_PRINT_BUFSIZE), false, NULL, true,
 		    arena_get(TSDN_NULL, 0, true), true);
-		buf_write_arg_t buf_arg;
-		buf_write_init(&buf_arg, write_cb, cbopaque, buf,
-		    STATS_PRINT_BUFSIZE);
-		stats_print(buf_write_cb, &buf_arg, opts);
-		buf_write_flush(&buf_arg);
-		idalloctm(tsdn, buf, NULL, NULL, true, true);
+		if (buf == NULL) {
+			stats_print(write_cb, cbopaque, opts);
+		} else {
+			buf_write_arg_t buf_arg;
+			buf_write_init(&buf_arg, write_cb, cbopaque, buf,
+			    STATS_PRINT_BUFSIZE);
+			stats_print(buf_write_cb, &buf_arg, opts);
+			buf_write_flush(&buf_arg);
+			idalloctm(tsdn, buf, NULL, NULL, true, true);
+		}
 	}
 
 	check_entry_exit_locking(tsdn);
diff --git a/src/prof_log.c b/src/prof_log.c
index 9495cf7a..a04c8e40 100644
--- a/src/prof_log.c
+++ b/src/prof_log.c
@@ -633,12 +633,15 @@ prof_log_stop(tsdn_t *tsdn) {
 	    sz_size2index(PROF_LOG_STOP_BUFSIZE), false, NULL, true,
 	    arena_get(TSDN_NULL, 0, true), true);
 	buf_write_arg_t buf_arg;
-	buf_write_init(&buf_arg, prof_emitter_write_cb, &arg, buf,
-	    PROF_LOG_STOP_BUFSIZE);
-
-	/* Emit to json. */
-	emitter_init(&emitter, emitter_output_json_compact, buf_write_cb,
-	    &buf_arg);
+	if (buf == NULL) {
+		emitter_init(&emitter, emitter_output_json_compact,
+		    prof_emitter_write_cb, &arg);
+	} else {
+		buf_write_init(&buf_arg, prof_emitter_write_cb, &arg, buf,
+		    PROF_LOG_STOP_BUFSIZE);
+		emitter_init(&emitter, emitter_output_json_compact,
+		    buf_write_cb, &buf_arg);
+	}
 
 	emitter_begin(&emitter);
 	prof_log_emit_metadata(&emitter);
@@ -647,8 +650,10 @@ prof_log_stop(tsdn_t *tsdn) {
 	prof_log_emit_allocs(tsd, &emitter);
 	emitter_end(&emitter);
 
-	buf_write_flush(&buf_arg);
-	idalloctm(tsdn, buf, NULL, NULL, true, true);
+	if (buf != NULL) {
+		buf_write_flush(&buf_arg);
+		idalloctm(tsdn, buf, NULL, NULL, true, true);
+	}
 
 	/* Reset global state. */
 	if (log_tables_initialized) {
diff --git a/src/prof_recent.c b/src/prof_recent.c
index a53f82c7..66a9b406 100644
--- a/src/prof_recent.c
+++ b/src/prof_recent.c
@@ -465,12 +465,17 @@ prof_recent_alloc_dump(tsd_t *tsd, void (*write_cb)(void *, const char *),
 	char *buf = (char *)iallocztm(tsd_tsdn(tsd), PROF_RECENT_PRINT_BUFSIZE,
 	    sz_size2index(PROF_RECENT_PRINT_BUFSIZE), false, NULL, true,
 	    arena_get(tsd_tsdn(tsd), 0, false), true);
-	buf_write_arg_t buf_arg;
-	buf_write_init(&buf_arg, write_cb, cbopaque, buf,
-	    PROF_RECENT_PRINT_BUFSIZE);
 	emitter_t emitter;
-	emitter_init(&emitter, emitter_output_json_compact, buf_write_cb,
-	    &buf_arg);
+	buf_write_arg_t buf_arg;
+	if (buf == NULL) {
+		emitter_init(&emitter, emitter_output_json_compact, write_cb,
+		    cbopaque);
+	} else {
+		buf_write_init(&buf_arg, write_cb, cbopaque, buf,
+		    PROF_RECENT_PRINT_BUFSIZE);
+		emitter_init(&emitter, emitter_output_json_compact,
+		    buf_write_cb, &buf_arg);
+	}
 	emitter_begin(&emitter);
 
 	malloc_mutex_lock(tsd_tsdn(tsd), &prof_recent_alloc_mtx);
@@ -530,8 +535,10 @@ prof_recent_alloc_dump(tsd_t *tsd, void (*write_cb)(void *, const char *),
 	malloc_mutex_unlock(tsd_tsdn(tsd), &prof_recent_alloc_mtx);
 
 	emitter_end(&emitter);
-	buf_write_flush(&buf_arg);
-	idalloctm(tsd_tsdn(tsd), buf, NULL, NULL, true, true);
+	if (buf != NULL) {
+		buf_write_flush(&buf_arg);
+		idalloctm(tsd_tsdn(tsd), buf, NULL, NULL, true, true);
+	}
 }
 #undef PROF_RECENT_PRINT_BUFSIZE