diff --git a/c-opopt.cc b/c-opopt.cc
index 06679a8..d5a8344 100644
--- a/c-opopt.cc
+++ b/c-opopt.cc
@@ -1503,7 +1503,7 @@ bool opopt::PropagateConstants(
 	T_Set< uint32_t > cDefs{ UseTag< ArrayBacked< 16 > >( ) };
 	T_AutoArray< double , 16 > cValues;
 	bool changesMade{ false };
-	for ( auto const& udc : oData.varUDChains.values( ) ) {
+	for ( auto& udc : oData.varUDChains.values( ) ) {
 		cDefs.clear( );
 		cValues.clear( );
 
@@ -1530,8 +1530,7 @@ bool opopt::PropagateConstants(
 			continue;
 		}
 
-		const auto nUses{ udc.uses.size( ) };
-		for ( auto i = 0u ; i < nUses ; i ++ ) {
+		for ( auto i = 0u ; i < udc.uses.size( ) ; ) {
 			auto const& use{ udc.uses[ i ] };
 			const auto nRefs{ use.refs.size( ) };
 			T_Optional< double > repVal{ };
@@ -1549,13 +1548,13 @@ bool opopt::PropagateConstants(
 				}
 			}
 			if ( !repVal ) {
+				i ++;
 				continue;
 			}
 
-			printf( "Could replace use at %d with constant %f\n" ,
-					use.node , *repVal );
 			CPReplaceWithConstant_( *oData.instructions[ use.node ].node ,
 					udc.var , *repVal , oData );
+			udc.uses.removeSwap( i );
 			changesMade = true;
 		}
 	}