diff --git a/CHANGELOG b/CHANGELOG
index 307dcc9e7b..f7860253a6 100644
--- a/CHANGELOG
+++ b/CHANGELOG
@@ -1,6 +1,12 @@
 v1.2.alpha (XXXX-XX-XX)
 -----------------------
 
+* replaced redundant error return code 1520 (Unable to open collection) with error code
+  1203 (Collection not found). These error codes have the same meanings, but one of
+  them was returned from AQL queries only, the other got thrown by other parts of
+  ArangoDB. Now, error 1203 (Collection not found) is used in AQL too in case a 
+  non-existing collection is used.
+
 * fixed issue #382: [Documentation error] Maschine... should be Machine...
  
 * unified history file locations for arangod, arangosh, and arangoirb.
diff --git a/arangod/Ahuacatl/ahuacatl-ast-node.c b/arangod/Ahuacatl/ahuacatl-ast-node.c
index f4da8c3348..ba353e2f30 100644
--- a/arangod/Ahuacatl/ahuacatl-ast-node.c
+++ b/arangod/Ahuacatl/ahuacatl-ast-node.c
@@ -398,7 +398,7 @@ TRI_aql_node_t* TRI_CreateNodeCollectionAql (TRI_aql_context_t* const context,
   }
   
   if (strlen(name) == 0) {
-    TRI_SetErrorContextAql(context, TRI_ERROR_QUERY_COLLECTION_NOT_FOUND, name);
+    TRI_SetErrorContextAql(context, TRI_ERROR_ARANGO_COLLECTION_NOT_FOUND, name);
 
     return NULL;
   }
diff --git a/arangod/Ahuacatl/ahuacatl-collections.c b/arangod/Ahuacatl/ahuacatl-collections.c
index 8a7f46e88e..6313c67dc7 100644
--- a/arangod/Ahuacatl/ahuacatl-collections.c
+++ b/arangod/Ahuacatl/ahuacatl-collections.c
@@ -159,7 +159,7 @@ bool OpenCollections (TRI_aql_context_t* const context) {
     LOG_TRACE("locking collection '%s'", collection->_name);
     collection->_collection = TRI_UseCollectionByNameVocBase(context->_vocbase, collection->_name);
     if (collection->_collection == NULL) {
-      TRI_SetErrorContextAql(context, TRI_ERROR_QUERY_COLLECTION_NOT_FOUND, collection->_name);
+      TRI_SetErrorContextAql(context, TRI_ERROR_ARANGO_COLLECTION_NOT_FOUND, collection->_name);
 
       return false;
     }
diff --git a/js/common/bootstrap/errors.js b/js/common/bootstrap/errors.js
index 82aa5492c3..7ca55dcedb 100644
--- a/js/common/bootstrap/errors.js
+++ b/js/common/bootstrap/errors.js
@@ -87,7 +87,6 @@
     "ERROR_QUERY_VARIABLE_NAME_INVALID" : { "code" : 1510, "message" : "variable name '%s' has an invalid format" }, 
     "ERROR_QUERY_VARIABLE_REDECLARED" : { "code" : 1511, "message" : "variable '%s' is assigned multiple times" }, 
     "ERROR_QUERY_VARIABLE_NAME_UNKNOWN" : { "code" : 1512, "message" : "unknown variable '%s'" }, 
-    "ERROR_QUERY_COLLECTION_NOT_FOUND" : { "code" : 1520, "message" : "unable to open collection '%s'" }, 
     "ERROR_QUERY_COLLECTION_LOCK_FAILED" : { "code" : 1521, "message" : "unable to read-lock collection %s" }, 
     "ERROR_QUERY_TOO_MANY_COLLECTIONS" : { "code" : 1522, "message" : "too many collections" }, 
     "ERROR_QUERY_DOCUMENT_ATTRIBUTE_REDECLARED" : { "code" : 1530, "message" : "document attribute '%s' is assigned multiple times" }, 
diff --git a/lib/BasicsC/errors.dat b/lib/BasicsC/errors.dat
index a27491d2a7..641ca1ea18 100755
--- a/lib/BasicsC/errors.dat
+++ b/lib/BasicsC/errors.dat
@@ -117,7 +117,6 @@ ERROR_QUERY_NUMBER_OUT_OF_RANGE,1504,"number out of range","Will be raised when
 ERROR_QUERY_VARIABLE_NAME_INVALID,1510,"variable name '%s' has an invalid format","Will be raised when an invalid variable name is used."
 ERROR_QUERY_VARIABLE_REDECLARED,1511,"variable '%s' is assigned multiple times","Will be raised when a variable gets re-assigned in a query."
 ERROR_QUERY_VARIABLE_NAME_UNKNOWN,1512,"unknown variable '%s'","Will be raised when an unknown variable is used or the variable is undefined the context it is used."
-ERROR_QUERY_COLLECTION_NOT_FOUND,1520,"unable to open collection '%s'","Will be raised when one of the collections referenced in the query was not found."
 ERROR_QUERY_COLLECTION_LOCK_FAILED,1521,"unable to read-lock collection %s","Will be raised when a read lock on the collection cannot be acquired."
 ERROR_QUERY_TOO_MANY_COLLECTIONS,1522,"too many collections","Will be raised when the number of collections in a query is beyond the allowed value."
 ERROR_QUERY_DOCUMENT_ATTRIBUTE_REDECLARED,1530,"document attribute '%s' is assigned multiple times","Will be raised when a document attribute is re-assigned."
diff --git a/lib/BasicsC/voc-errors.c b/lib/BasicsC/voc-errors.c
index 4fdda30535..6976a4beb1 100644
--- a/lib/BasicsC/voc-errors.c
+++ b/lib/BasicsC/voc-errors.c
@@ -83,7 +83,6 @@ void TRI_InitialiseErrorMessages (void) {
   REG_ERROR(ERROR_QUERY_VARIABLE_NAME_INVALID, "variable name '%s' has an invalid format");
   REG_ERROR(ERROR_QUERY_VARIABLE_REDECLARED, "variable '%s' is assigned multiple times");
   REG_ERROR(ERROR_QUERY_VARIABLE_NAME_UNKNOWN, "unknown variable '%s'");
-  REG_ERROR(ERROR_QUERY_COLLECTION_NOT_FOUND, "unable to open collection '%s'");
   REG_ERROR(ERROR_QUERY_COLLECTION_LOCK_FAILED, "unable to read-lock collection %s");
   REG_ERROR(ERROR_QUERY_TOO_MANY_COLLECTIONS, "too many collections");
   REG_ERROR(ERROR_QUERY_DOCUMENT_ATTRIBUTE_REDECLARED, "document attribute '%s' is assigned multiple times");
diff --git a/lib/BasicsC/voc-errors.h b/lib/BasicsC/voc-errors.h
index 81a50a33cd..78e4bd2cf7 100644
--- a/lib/BasicsC/voc-errors.h
+++ b/lib/BasicsC/voc-errors.h
@@ -173,9 +173,6 @@ extern "C" {
 /// - 1512: @LIT{unknown variable '\%s'}
 ///   Will be raised when an unknown variable is used or the variable is
 ///   undefined the context it is used.
-/// - 1520: @LIT{unable to open collection '\%s'}
-///   Will be raised when one of the collections referenced in the query was
-///   not found.
 /// - 1521: @LIT{unable to read-lock collection \%s}
 ///   Will be raised when a read lock on the collection cannot be acquired.
 /// - 1522: @LIT{too many collections}
@@ -1096,17 +1093,6 @@ void TRI_InitialiseErrorMessages (void);
 
 #define TRI_ERROR_QUERY_VARIABLE_NAME_UNKNOWN                             (1512)
 
-////////////////////////////////////////////////////////////////////////////////
-/// @brief 1520: ERROR_QUERY_COLLECTION_NOT_FOUND
-///
-/// unable to open collection '%s'
-///
-/// Will be raised when one of the collections referenced in the query was not
-/// found.
-////////////////////////////////////////////////////////////////////////////////
-
-#define TRI_ERROR_QUERY_COLLECTION_NOT_FOUND                              (1520)
-
 ////////////////////////////////////////////////////////////////////////////////
 /// @brief 1521: ERROR_QUERY_COLLECTION_LOCK_FAILED
 ///