diff --git a/src/org/rascalmpl/interpreter/matching/TypedVariablePattern.java b/src/org/rascalmpl/interpreter/matching/TypedVariablePattern.java
index 6e3ccdb6c26..e94a28eddaa 100644
--- a/src/org/rascalmpl/interpreter/matching/TypedVariablePattern.java
+++ b/src/org/rascalmpl/interpreter/matching/TypedVariablePattern.java
@@ -113,7 +113,7 @@ public boolean next() {
 					
 					if (dynMatchType.isOpen()) {
 						// type parameter hygiene required (consider self-application of a function like `&T id(&T v) = v`)
-						dynMatchType = AbstractFunction.renameType(dynMatchType, new HashMap<>(), Integer.toString(ctx.getCurrentAST().getLocation().getOffset()));
+						dynMatchType = AbstractFunction.renameType(dynMatchType, new HashMap<>(), ctx.getCurrentAST().getLocation());
 					}
 
 					if (!declaredType.match(dynMatchType, dynBindings)) {
@@ -134,7 +134,7 @@ public boolean next() {
 			Type dynType = subject.getValue().getType();
 			if (dynType.isOpen()) {
 				// type parameter hygiene required (consider self-application of a function like `&T id(&T v) = v`)
-				dynType = AbstractFunction.renameType(dynType, new HashMap<>(), Integer.toString(ctx.getCurrentAST().getLocation().getOffset()));
+				dynType = AbstractFunction.renameType(dynType, new HashMap<>(), ctx.getCurrentAST().getLocation());
 			}
 
 			if (!dynType.isSubtypeOf(declaredType.instantiate(ctx.getCurrentEnvt().getDynamicTypeBindings()))) {
diff --git a/src/org/rascalmpl/interpreter/result/AbstractFunction.java b/src/org/rascalmpl/interpreter/result/AbstractFunction.java
index c68b5beccda..a0a29e38fc2 100644
--- a/src/org/rascalmpl/interpreter/result/AbstractFunction.java
+++ b/src/org/rascalmpl/interpreter/result/AbstractFunction.java
@@ -43,6 +43,7 @@
 import io.usethesource.vallang.IConstructor;
 import io.usethesource.vallang.IExternalValue;
 import io.usethesource.vallang.IListWriter;
+import io.usethesource.vallang.ISourceLocation;
 import io.usethesource.vallang.IValue;
 import io.usethesource.vallang.IValueFactory;
 import io.usethesource.vallang.IWithKeywordParameters;
@@ -345,7 +346,7 @@ protected Type bindTypeParameters(Type actualStaticTypes, IValue[] actuals, Type
 		    if (actualStaticTypes.isOpen()) {
 			    // we have to make the environment hygenic now, because the caller scope
 			    // may have the same type variable names as the current scope
-			    actualStaticTypes = renameType(actualStaticTypes, renamings, Integer.toString(env.getLocation().getOffset()));
+			    actualStaticTypes = renameType(actualStaticTypes, renamings, env.getLocation());
 			}
 
 			
@@ -393,7 +394,7 @@ protected static Type unrenameType(Map<Type, Type> renamings, Type resultType) {
 	    return resultType;
 	}
 	  
-    public static Type renameType(Type actualTypes, Map<Type, Type> renamings, String uniquePrefix) {
+    public static Type renameType(Type actualTypes, Map<Type, Type> renamings, ISourceLocation uniquePrefix) {
         actualTypes.match(TypeFactory.getInstance().voidType(), renamings);
         
         // rename all the bound type parameters
diff --git a/src/org/rascalmpl/interpreter/result/NamedFunction.java b/src/org/rascalmpl/interpreter/result/NamedFunction.java
index 9523c20c6a1..4323f410129 100644
--- a/src/org/rascalmpl/interpreter/result/NamedFunction.java
+++ b/src/org/rascalmpl/interpreter/result/NamedFunction.java
@@ -164,7 +164,7 @@ protected void checkReturnTypeIsNotVoid(List<Expression> formals, IValue[] actua
         Map<Type, Type> bindings = new HashMap<>();
         
         for (int i = 0; i < actuals.length; i++) {
-            formals.get(i).typeOf(declarationEnvironment, getEval(), false).match(renameType(actuals[i].getType(), renamings, Integer.toString(ctx.getCurrentAST().getLocation().getOffset())), bindings);
+            formals.get(i).typeOf(declarationEnvironment, getEval(), false).match(renameType(actuals[i].getType(), renamings, ctx.getCurrentAST().getLocation()), bindings);
         }
         
         if (!getReturnType().isBottom() && getReturnType().instantiate(bindings).isBottom()) {