diff --git a/arangod/Aql/ExecutionBlock.cpp b/arangod/Aql/ExecutionBlock.cpp
index 05bed20f14..1a2456133b 100644
--- a/arangod/Aql/ExecutionBlock.cpp
+++ b/arangod/Aql/ExecutionBlock.cpp
@@ -3635,7 +3635,7 @@ AqlItemBlock* GatherBlock::getSome (size_t atLeast, size_t atMost) {
  
   // the non-simple case . . .
   size_t available = 0; // nr of available rows
-  size_t index;         // an index of a non-empty buffer
+  size_t index = 0;     // an index of a non-empty buffer
   
   // pull more blocks from dependencies . . .
   for (size_t i = 0; i < _dependencies.size(); i++) {