diff --git a/eeschema/tools/ee_selection_tool.cpp b/eeschema/tools/ee_selection_tool.cpp
index 31f96ec856..fccac45df6 100644
--- a/eeschema/tools/ee_selection_tool.cpp
+++ b/eeschema/tools/ee_selection_tool.cpp
@@ -173,7 +173,7 @@ bool EE_SELECTION_TOOL::Init()
                 if( m_isSymbolEditor || m_isSymbolViewer )
                     return false;
 
-                return ( E_C::Empty( aSel ) || sheetSelection( aSel ) );
+                return E_C::LessThan( 2 )( aSel ) && E_C::OnlyType( SCH_SHEET_T )( aSel );
             };
 
     auto schEditCondition =
diff --git a/include/tool/selection_conditions.h b/include/tool/selection_conditions.h
index e804f8498f..fc68aa1b4b 100644
--- a/include/tool/selection_conditions.h
+++ b/include/tool/selection_conditions.h
@@ -41,6 +41,7 @@ SELECTION_CONDITION operator||( const SELECTION_CONDITION& aConditionA,
 SELECTION_CONDITION operator&&( const SELECTION_CONDITION& aConditionA,
                                 const SELECTION_CONDITION& aConditionB );
 
+SELECTION_CONDITION operator!( const SELECTION_CONDITION& aCondition );
 
 
 /// Signature for a reference to a function that takes a SELECTION and returns
@@ -61,6 +62,15 @@ SELECTION_CONDITION operator&&( const SELECTION_CONDITION& aConditionA,
 SELECTION_CONDITION operator&&( SELECTION_BOOL aConditionA,
                                 const SELECTION_CONDITION& aConditionB );
 
+// We don't use uninitialized SELECTION_CONDITIONs, so casting to bool is probably
+// a programming error.
+template<> SELECTION_CONDITION::operator bool() const noexcept
+{
+    wxASSERT( "Incorrect use of SELECTION_CONDITION" );
+    return false;
+};
+
+
 /**
  * Class that groups generic conditions for selected items.
  */