diff --git a/src/org/rascalmpl/semantics/dynamic/PathPart.java b/src/org/rascalmpl/semantics/dynamic/PathPart.java
index b2a4def8fbc..4230b59f133 100644
--- a/src/org/rascalmpl/semantics/dynamic/PathPart.java
+++ b/src/org/rascalmpl/semantics/dynamic/PathPart.java
@@ -12,14 +12,21 @@
 *******************************************************************************/
 package org.rascalmpl.semantics.dynamic;
 
+import java.net.URI;
+import java.net.URISyntaxException;
+
 import org.rascalmpl.ast.Expression;
 import org.rascalmpl.ast.PathChars;
 import org.rascalmpl.ast.PathTail;
 import org.rascalmpl.ast.PrePathChars;
+import org.rascalmpl.exceptions.RuntimeExceptionFactory;
 import org.rascalmpl.interpreter.IEvaluator;
 import org.rascalmpl.interpreter.result.Result;
+import org.rascalmpl.interpreter.result.ResultFactory;
+import org.rascalmpl.uri.URIUtil;
 import io.usethesource.vallang.IConstructor;
 import io.usethesource.vallang.ISourceLocation;
+import io.usethesource.vallang.IString;
 import io.usethesource.vallang.IValue;
 
 public abstract class PathPart extends org.rascalmpl.ast.PathPart {
@@ -37,9 +44,29 @@ public Result<IValue> interpret(IEvaluator<Result<IValue>> __eval) {
 
 			Result<IValue> pre = this.getPre().interpret(__eval);
 			Result<IValue> expr = this.getExpression().interpret(__eval);
-			Result<IValue> tail = this.getTail().interpret(__eval);
-
-			return pre.add(expr).add(tail);
+			// here we have to encode the string for us in the path part of a uri
+			// the trick is to use new File which does the encoding for us, in 
+			// a way that conforms to the current OS where we are running. So if someone
+			// is splicing a windows path here, with the slashes the other way around,
+			// they are first interpreted as path separators and not encoded as %slash
+			// However, first we need to map the expression result to string by using
+			// the `add` semantics of strings:
+			IString path = (IString) ResultFactory.makeResult(TF.stringType(), VF.string(""), __eval)
+				.add(expr).getValue();
+			
+			try {
+				// reuse our URI encoders here on the unencoded expression part 
+				URI tmp = URIUtil.create("x", "", "/" + path.getValue());
+				// but get the path out directly anyway, unencoded!
+				path = VF.string(tmp.getRawPath());
+
+				// connect the pre, middle and end pieces
+				Result<IValue> tail = this.getTail().interpret(__eval);
+				return pre.add(ResultFactory.makeResult(TF.stringType(), path, __eval)).add(tail);
+			}
+			catch (URISyntaxException e) {
+				throw RuntimeExceptionFactory.malformedURI(path.getValue(), getExpression(), __eval.getStackTrace());
+			}
 		}
 
 	}
diff --git a/src/org/rascalmpl/semantics/dynamic/PathTail.java b/src/org/rascalmpl/semantics/dynamic/PathTail.java
index ebe8a3807b7..17cfaaae30c 100644
--- a/src/org/rascalmpl/semantics/dynamic/PathTail.java
+++ b/src/org/rascalmpl/semantics/dynamic/PathTail.java
@@ -12,13 +12,21 @@
 *******************************************************************************/
 package org.rascalmpl.semantics.dynamic;
 
+import java.net.URI;
+import java.net.URISyntaxException;
+
 import org.rascalmpl.ast.Expression;
 import org.rascalmpl.ast.MidPathChars;
 import org.rascalmpl.ast.PostPathChars;
+import org.rascalmpl.exceptions.RuntimeExceptionFactory;
 import org.rascalmpl.interpreter.IEvaluator;
 import org.rascalmpl.interpreter.result.Result;
+import org.rascalmpl.interpreter.result.ResultFactory;
+import org.rascalmpl.uri.URIUtil;
+
 import io.usethesource.vallang.IConstructor;
 import io.usethesource.vallang.ISourceLocation;
+import io.usethesource.vallang.IString;
 import io.usethesource.vallang.IValue;
 
 public abstract class PathTail extends org.rascalmpl.ast.PathTail {
@@ -34,9 +42,23 @@ public Mid(ISourceLocation __param1, IConstructor tree, MidPathChars __param2, E
 		public Result<IValue> interpret(IEvaluator<Result<IValue>> __eval) {
 			Result<IValue> mid = this.getMid().interpret(__eval);
 			Result<IValue> expr = this.getExpression().interpret(__eval);
-			Result<IValue> tail = this.getTail().interpret(__eval);
 
-			return mid.add(expr).add(tail);
+			IString path = (IString) ResultFactory.makeResult(TF.stringType(), VF.string(""), __eval)
+				.add(expr).getValue();
+			
+			try {
+				// reuse our URI encoders here on the unencoded expression part 
+				URI tmp = URIUtil.create("x", "", "/" + path.getValue());
+				// but get the path out directly anyway, unencoded!
+				path = VF.string(tmp.getRawPath());
+
+				// connect the pre, middle and end pieces
+				Result<IValue> tail = this.getTail().interpret(__eval);
+				return mid.add(ResultFactory.makeResult(TF.stringType(), path, __eval)).add(tail);
+			}
+			catch (URISyntaxException e) {
+				throw RuntimeExceptionFactory.malformedURI(path.getValue(), getExpression(), __eval.getStackTrace());
+			}
 		}
 
 	}