diff --git a/include/common/buf.h b/include/common/buf.h
index 1051229a..2cd97e35 100644
--- a/include/common/buf.h
+++ b/include/common/buf.h
@@ -34,7 +34,7 @@ void buf_expand_shell_variables(struct buf *s);
 /**
  * buf_init - allocate NULL-terminated C string buffer
  * @s: buffer
- * Note: use free(s->buf) to free it
+ * Note: use buf_finish(buf) to free it
  */
 void buf_init(struct buf *s);
 
@@ -55,13 +55,41 @@ void buf_add_char(struct buf *s, char data);
 /**
  * buf_clear - clear the buffer, internal allocations are preserved
  * @s: buffer
+ *
+ * This is the appropriate function to call to re-use the buffer
+ * in a loop or similar situations as it simply reuses the already
+ * existing heap allocations.
  */
 void buf_clear(struct buf *s);
 
 /**
  * buf_reset - reset the buffer, internal allocations are free'd
  * @s: buffer
+ *
+ * The buffer will automatically be re-initialized so can be used again.
+ *
+ * This function should not be used in loops as it will free and then
+ * re-allocate heap memory. However, if the buffer becomes too big
+ * and the internal allocation should be free'd this is the correct
+ * function to use.
  */
 void buf_reset(struct buf *s);
 
+/**
+ * buf_finish - free all internal allocations
+ * @s: buffer
+ *
+ * The state of the buffer after this call is undefined.
+ * It can be re-initalized via buf_init() however.
+ *
+ * Use this for the usual case of a stack allocated buf instance:
+ *   struct buf buf;
+ *   buf_init(&buf);
+ *   buf_add(&buf, "some");
+ *   buf_add(&buf, "thing");
+ *   do_something_with(buf.buf);
+ *   buf_finish(&buf);
+ */
+void buf_finish(struct buf *s);
+
 #endif /* LABWC_BUF_H */
diff --git a/src/action.c b/src/action.c
index 3723e42b..25281ab1 100644
--- a/src/action.c
+++ b/src/action.c
@@ -709,7 +709,7 @@ actions_run(struct view *activator, struct server *server,
 				buf_add(&cmd, action_get_str(action, "command", NULL));
 				buf_expand_tilde(&cmd);
 				spawn_async_no_shell(cmd.buf);
-				free(cmd.buf);
+				buf_finish(&cmd);
 			}
 			break;
 		case ACTION_TYPE_EXIT:
diff --git a/src/common/buf.c b/src/common/buf.c
index f6bde97f..37505d5f 100644
--- a/src/common/buf.c
+++ b/src/common/buf.c
@@ -69,7 +69,7 @@ buf_expand_shell_variables(struct buf *s)
 			buf_add_char(&new, s->buf[i]);
 		}
 	}
-	free(environment_variable.buf);
+	buf_finish(&environment_variable);
 	free(s->buf);
 	s->buf = new.buf;
 	s->len = new.len;
@@ -79,7 +79,10 @@ buf_expand_shell_variables(struct buf *s)
 void
 buf_init(struct buf *s)
 {
-	/* we can't assert(!s->buf) here because struct may be uninitialized */
+	/*
+	 * We can't assert(!s->buf) here because
+	 * the supplied struct may be uninitialized.
+	 */
 
 	s->alloc = 256;
 	s->buf = xmalloc(s->alloc);
@@ -130,6 +133,21 @@ buf_clear(struct buf *s)
 void
 buf_reset(struct buf *s)
 {
-	zfree(s->buf);
+	assert(s->buf);
+
+	buf_finish(s);
 	buf_init(s);
 }
+
+void
+buf_finish(struct buf *s)
+{
+	assert(s->buf);
+
+	/*
+	 * Using zfree rather than free ensures that the
+	 * asserts will be triggered whenever something
+	 * other than buf_init() is called on the buffer.
+	 */
+	zfree(s->buf);
+}
diff --git a/src/common/dir.c b/src/common/dir.c
index 59db4104..d474c313 100644
--- a/src/common/dir.c
+++ b/src/common/dir.c
@@ -100,7 +100,7 @@ find_dir(struct ctx *ctx)
 		char *pfxenv = getenv(d.prefix);
 		buf_add(&prefix, pfxenv ? pfxenv : d.default_prefix);
 		if (!prefix.len) {
-			free(prefix.buf);
+			buf_finish(&prefix);
 			continue;
 		}
 
@@ -130,7 +130,7 @@ find_dir(struct ctx *ctx)
 			wl_list_append(ctx->list, &path->link);
 		}
 		g_strfreev(prefixes);
-		free(prefix.buf);
+		buf_finish(&prefix);
 	}
 }
 
diff --git a/src/config/rcxml.c b/src/config/rcxml.c
index d6a926d0..c1ed4801 100644
--- a/src/config/rcxml.c
+++ b/src/config/rcxml.c
@@ -1539,7 +1539,7 @@ rcxml_read(const char *filename)
 		zfree(line);
 		fclose(stream);
 		rcxml_parse_xml(&b);
-		zfree(b.buf);
+		buf_finish(&b);
 		if (!should_merge_config) {
 			break;
 		}
diff --git a/src/config/session.c b/src/config/session.c
index ee56b548..3da3898b 100644
--- a/src/config/session.c
+++ b/src/config/session.c
@@ -55,7 +55,7 @@ process_line(char *line)
 	buf_expand_shell_variables(&value);
 	buf_expand_tilde(&value);
 	setenv(key, value.buf, 1);
-	free(value.buf);
+	buf_finish(&value);
 }
 
 /* return true on successful read */
diff --git a/src/menu/menu.c b/src/menu/menu.c
index 822f5932..37bcef51 100644
--- a/src/menu/menu.c
+++ b/src/menu/menu.c
@@ -543,7 +543,7 @@ parse(struct server *server, FILE *stream)
 	xmlFreeDoc(d);
 	xmlCleanupParser();
 err:
-	free(b.buf);
+	buf_finish(&b);
 }
 
 static void
diff --git a/src/osd.c b/src/osd.c
index 85e9f433..b66a9eb2 100644
--- a/src/osd.c
+++ b/src/osd.c
@@ -442,7 +442,7 @@ render_osd(struct server *server, cairo_t *cairo, int w, int h,
 
 		y += theme->osd_window_switcher_item_height;
 	}
-	free(buf.buf);
+	buf_finish(&buf);
 	g_object_unref(layout);
 
 	cairo_surface_flush(surf);