diff --git a/src/glsl/ir.h b/src/glsl/ir.h
index 535693d9273..5032c2610fa 100644
--- a/src/glsl/ir.h
+++ b/src/glsl/ir.h
@@ -688,6 +688,15 @@ public:
        */
       unsigned must_be_shader_input:1;
 
+      /**
+       * Output index for dual source blending.
+       *
+       * \note
+       * The GLSL spec only allows the values 0 or 1 for the index in \b dual
+       * source blending.
+       */
+      unsigned index:1;
+
       /**
        * \brief Layout qualifier for gl_FragDepth.
        *
@@ -721,11 +730,6 @@ public:
        */
       unsigned stream;
 
-      /**
-       * output index for dual source blending.
-       */
-      int index;
-
       /**
        * Initial binding point for a sampler, atomic, or UBO.
        *