diff --git a/src/mesa/drivers/dri/i965/brw_vec4.cpp b/src/mesa/drivers/dri/i965/brw_vec4.cpp
index f9565de5118..a4385e6ca69 100644
--- a/src/mesa/drivers/dri/i965/brw_vec4.cpp
+++ b/src/mesa/drivers/dri/i965/brw_vec4.cpp
@@ -1105,11 +1105,13 @@ vec4_visitor::opt_register_coalesce()
 	 if (interfered)
 	    break;
 
-         /* If somebody else writes our destination here, we can't coalesce
-          * before that.
+         /* If somebody else writes the same channels of our destination here,
+          * we can't coalesce before that.
           */
-         if (inst->dst.in_range(scan_inst->dst, scan_inst->regs_written))
-	    break;
+         if (inst->dst.in_range(scan_inst->dst, scan_inst->regs_written) &&
+             (inst->dst.writemask & scan_inst->dst.writemask) != 0) {
+            break;
+         }
 
          /* Check for reads of the register we're trying to coalesce into.  We
           * can't go rewriting instructions above that to put some other value