diff --git a/core/internal/windowrules/providers/niri_parser.go b/core/internal/windowrules/providers/niri_parser.go
index 2f991cee..5bb5ec45 100644
--- a/core/internal/windowrules/providers/niri_parser.go
+++ b/core/internal/windowrules/providers/niri_parser.go
@@ -864,10 +864,12 @@ func (p *NiriWritableProvider) formatRule(rule windowrules.WindowRule) string {
 
 func formatSizeProperty(name, value string) string {
 	parts := strings.SplitN(value, " ", 2)
-	if len(parts) != 2 {
-		return fmt.Sprintf("    %s { }", name)
+	if len(parts) == 2 {
+		return fmt.Sprintf("    %s { %s %s; }", name, parts[0], parts[1])
 	}
-	sizeType := parts[0]
-	sizeValue := parts[1]
-	return fmt.Sprintf("    %s { %s %s; }", name, sizeType, sizeValue)
+	// Bare number without type prefix — default to "fixed"
+	if _, err := strconv.Atoi(value); err == nil {
+		return fmt.Sprintf("    %s { fixed %s; }", name, value)
+	}
+	return fmt.Sprintf("    %s { }", name)
 }
diff --git a/quickshell/Modals/WindowRuleModal.qml b/quickshell/Modals/WindowRuleModal.qml
index 7490333c..6c9583aa 100644
--- a/quickshell/Modals/WindowRuleModal.qml
+++ b/quickshell/Modals/WindowRuleModal.qml
@@ -631,7 +631,7 @@ FloatingWindow {
                                 anchors.fill: parent
                                 font.pixelSize: Theme.fontSizeSmall
                                 textColor: Theme.surfaceText
-                                placeholderText: "fixed 800"
+                                placeholderText: "800"
                                 backgroundColor: "transparent"
                                 enabled: root.visible
                             }
@@ -658,7 +658,7 @@ FloatingWindow {
                                 anchors.fill: parent
                                 font.pixelSize: Theme.fontSizeSmall
                                 textColor: Theme.surfaceText
-                                placeholderText: "fixed 600"
+                                placeholderText: "600"
                                 backgroundColor: "transparent"
                                 enabled: root.visible
                             }