diff --git a/src/providers/postgres/qgspostgresprovider.cpp b/src/providers/postgres/qgspostgresprovider.cpp
index c7a0208006a..0625fd264d2 100644
--- a/src/providers/postgres/qgspostgresprovider.cpp
+++ b/src/providers/postgres/qgspostgresprovider.cpp
@@ -1054,9 +1054,9 @@ bool QgsPostgresProvider::loadFields()
     QgsField newField = QgsField( fieldName, fieldType, fieldTypeName, fieldSize, fieldPrec, fieldComment, fieldSubType );
 
     QgsFieldConstraints constraints;
-    if ( notNullMap[tableoid][attnum] || mPrimaryKeyAttrs.contains( i ) )
+    if ( notNullMap[tableoid][attnum] || ( mPrimaryKeyAttrs.size() == 1 && mPrimaryKeyAttrs[0] == i ) || identityMap[tableoid][attnum] != ' ' )
       constraints.setConstraint( QgsFieldConstraints::ConstraintNotNull, QgsFieldConstraints::ConstraintOriginProvider );
-    if ( uniqueMap[tableoid][attnum] || mPrimaryKeyAttrs.contains( i ) )
+    if ( uniqueMap[tableoid][attnum] || ( mPrimaryKeyAttrs.size() == 1 && mPrimaryKeyAttrs[0] == i ) || identityMap[tableoid][attnum] != ' ' )
       constraints.setConstraint( QgsFieldConstraints::ConstraintUnique, QgsFieldConstraints::ConstraintOriginProvider );
     newField.setConstraints( constraints );
 
@@ -1453,13 +1453,13 @@ bool QgsPostgresProvider::determinePrimaryKey()
     determinePrimaryKeyFromUriKeyColumn();
   }
 
-  Q_FOREACH ( int fieldIdx, mPrimaryKeyAttrs )
+  if ( mPrimaryKeyAttrs.size() == 1 )
   {
     //primary keys are unique, not null
-    QgsFieldConstraints constraints = mAttributeFields.at( fieldIdx ).constraints();
+    QgsFieldConstraints constraints = mAttributeFields.at( mPrimaryKeyAttrs[0] ).constraints();
     constraints.setConstraint( QgsFieldConstraints::ConstraintUnique, QgsFieldConstraints::ConstraintOriginProvider );
     constraints.setConstraint( QgsFieldConstraints::ConstraintNotNull, QgsFieldConstraints::ConstraintOriginProvider );
-    mAttributeFields[ fieldIdx ].setConstraints( constraints );
+    mAttributeFields[ mPrimaryKeyAttrs[0] ].setConstraints( constraints );
   }
 
   mValid = mPrimaryKeyType != PktUnknown;