diff --git a/protocol/wayland.dtd b/protocol/wayland.dtd
index ae8340d6..7e54b0f9 100644
--- a/protocol/wayland.dtd
+++ b/protocol/wayland.dtd
@@ -25,6 +25,7 @@
   <!ATTLIST entry summary CDATA #IMPLIED>
   <!ATTLIST entry since CDATA #IMPLIED>
   <!ATTLIST entry deprecated-since CDATA #IMPLIED>
+  <!ATTLIST entry valid-zero CDATA #IMPLIED>
 <!ELEMENT arg (description?)>
   <!ATTLIST arg name CDATA #REQUIRED>
   <!ATTLIST arg type CDATA #REQUIRED>
diff --git a/protocol/wayland.xml b/protocol/wayland.xml
index 513b8fd8..0e10f3ec 100644
--- a/protocol/wayland.xml
+++ b/protocol/wayland.xml
@@ -1117,7 +1117,7 @@
         or drags initiated with other buttons than BTN_LEFT to specific
         actions (e.g. "ask").
       </description>
-      <entry name="none" value="0" summary="no action"/>
+      <entry name="none" value="0" summary="no action" valid-zero="true"/>
       <entry name="copy" value="1" summary="copy action"/>
       <entry name="move" value="2" summary="move action"/>
       <entry name="ask" value="4" summary="ask action"/>
@@ -1205,7 +1205,7 @@
         use this information to adapt its behavior, e.g. choose
         an appropriate cursor image.
       </description>
-      <entry name="none" value="0" summary="no edge"/>
+      <entry name="none" value="0" summary="no edge" valid-zero="true"/>
       <entry name="top" value="1" summary="top edge"/>
       <entry name="bottom" value="2" summary="bottom edge"/>
       <entry name="left" value="4" summary="left edge"/>
diff --git a/src/scanner.c b/src/scanner.c
index cd5f7fea..2e5cfa87 100644
--- a/src/scanner.c
+++ b/src/scanner.c
@@ -738,6 +738,7 @@ start_element(void *data, const char *element_name, const char **atts)
 	const char *bitfield = NULL;
 	const char *frozen = NULL;
 	int i, version = 0;
+	bool valid_zero = false;
 
 	ctx->loc.line_number = XML_GetCurrentLineNumber(ctx->parser);
 	for (i = 0; atts[i]; i += 2) {
@@ -762,6 +763,14 @@ start_element(void *data, const char *element_name, const char **atts)
 			deprecated_since = atts[i + 1];
 		if (strcmp(atts[i], "allow-null") == 0)
 			allow_null = atts[i + 1];
+		if (strcmp(atts[i], "valid-zero") == 0) {
+			if (strcmp(atts[i + 1], "true") == 0)
+				valid_zero = true;
+			else
+				fail(&ctx->loc,
+				     "Invalid value for valid-zero: %s",
+				     atts[i + 1]);
+		}
 		if (strcmp(atts[i], "enum") == 0)
 			enumeration_name = atts[i + 1];
 		if (strcmp(atts[i], "bitfield") == 0)
@@ -931,6 +940,9 @@ start_element(void *data, const char *element_name, const char **atts)
 			     version, entry->since);
 		entry->deprecated_since = version;
 
+		if (ctx->enumeration->bitfield && !valid_zero && strcmp(entry->value, "0") == 0)
+			warn(&ctx->loc, "value 0 used in a bitfield entry");
+
 		if (summary)
 			entry->summary = xstrdup(summary);
 		else