diff --git a/src/compiler/ParseHelper.cpp b/src/compiler/ParseHelper.cpp
index 31af70d..e49ae7c 100644
--- a/src/compiler/ParseHelper.cpp
+++ b/src/compiler/ParseHelper.cpp
@@ -2028,6 +2028,11 @@
                 error(location, "", "[", "array indexes for interface blocks arrays must be constant integeral expressions");
                 recover();
             }
+            else if (baseExpression->getQualifier() == EvqFragmentOutput)
+            {
+                error(location, "", "[", "array indexes for output variables must be constant integeral expressions");
+                recover();
+            }
 
             indexedExpression = intermediate.addIndex(EOpIndexIndirect, baseExpression, indexExpression, location);
         }