diff --git a/src/main/java/de/neemann/digital/core/extern/handler/GHDLProcess.java b/src/main/java/de/neemann/digital/core/extern/handler/GHDLProcess.java
index 37b479e10..b40dd621c 100644
--- a/src/main/java/de/neemann/digital/core/extern/handler/GHDLProcess.java
+++ b/src/main/java/de/neemann/digital/core/extern/handler/GHDLProcess.java
@@ -9,6 +9,7 @@ import de.neemann.digital.core.extern.PortDefinition;
 
 import java.io.File;
 import java.io.IOException;
+import java.util.LinkedList;
 
 /**
  * Can use GHDL as VHDL simulator.
@@ -51,4 +52,14 @@ public class GHDLProcess extends VHDLProcess {
             return false;
         }
     }
+
+    @Override
+    public String getConsoleOutNoWarn(LinkedList<String> consoleOut) {
+        StringBuilder sb = new StringBuilder();
+        for (String s : consoleOut) {
+            if (!s.contains("(assertion warning)"))
+                sb.append(s).append("\n");
+        }
+        return sb.toString();
+    }
 }
diff --git a/src/main/java/de/neemann/digital/core/extern/handler/StdIOProcess.java b/src/main/java/de/neemann/digital/core/extern/handler/StdIOProcess.java
index 568e173af..942fb4f6a 100644
--- a/src/main/java/de/neemann/digital/core/extern/handler/StdIOProcess.java
+++ b/src/main/java/de/neemann/digital/core/extern/handler/StdIOProcess.java
@@ -19,6 +19,7 @@ import java.util.LinkedList;
 public class StdIOProcess implements ProcessHandler {
     private static final String PREFIX = "Digital:";
     private static final int MAX_CONSOLE_LINES = 30;
+    private static final long TIMEOUT = 5000;
     private Process process;
     private BufferedWriter writer;
     private Thread thread;
@@ -26,6 +27,7 @@ public class StdIOProcess implements ProcessHandler {
 
     private final Object lock = new Object();
     private String dataFound;
+    private boolean terminated = false;
 
 
     /**
@@ -60,6 +62,7 @@ public class StdIOProcess implements ProcessHandler {
     private void setReaderWriter(BufferedReader reader, BufferedWriter writer) {
         this.writer = writer;
         consoleOut = new LinkedList<>();
+        terminated = false;
         thread = new Thread(() -> {
             try {
                 String line;
@@ -79,6 +82,10 @@ public class StdIOProcess implements ProcessHandler {
             } catch (IOException | InterruptedException e) {
                 e.printStackTrace();
             }
+            synchronized (lock) {
+                terminated = true;
+                lock.notify();
+            }
         });
         thread.setDaemon(true);
         thread.start();
@@ -88,10 +95,13 @@ public class StdIOProcess implements ProcessHandler {
         synchronized (lock) {
             try {
                 long startTime = System.currentTimeMillis();
-                while (dataFound == null && (System.currentTimeMillis() - startTime) < 5000)
+                long time = 0;
+                while (dataFound == null && !terminated && (time - startTime) < TIMEOUT) {
                     lock.wait(1000);
+                    time = System.currentTimeMillis();
+                }
 
-                if (dataFound == null)
+                if (!((time - startTime) < TIMEOUT))
                     throw new IOException(Lang.get("err_timeoutReadingData_O", getConsoleOut()));
 
                 String line = dataFound;
@@ -168,7 +178,18 @@ public class StdIOProcess implements ProcessHandler {
                 v.set(value, highZ);
             }
         } else
-            throw new IOException(Lang.get("err_processTerminatedUnexpected_O", getConsoleOut()));
+            throw new IOException(Lang.get("err_processTerminatedUnexpected_O", getConsoleOutNoWarn(consoleOut)));
+    }
+
+    /**
+     * Returns the console out without warnings.
+     * Used to remove not needed content which obfuscates the real error cause.
+     *
+     * @param consoleOut the console out
+     * @return the clean error message
+     */
+    public String getConsoleOutNoWarn(LinkedList<String> consoleOut) {
+        return getConsoleOut();
     }
 
     private String getConsoleOut() {
diff --git a/src/test/resources/dig/external/ghdl.dig b/src/test/resources/dig/external/ghdl.dig
index 22d93c9b6..cfef78210 100644
--- a/src/test/resources/dig/external/ghdl.dig
+++ b/src/test/resources/dig/external/ghdl.dig
@@ -44,7 +44,7 @@ end add;
 architecture add_arch of add is
    signal temp : std_logic_vector(4 downto 0);
 begin
-   temp &lt;= (&apos;0&apos; &amp; a) + (&apos;0&apos; &amp; b) + (&apos;0&apos; &amp; c_i);
+   temp &lt;= (&apos;0&apos; &amp; a) + b + c_i;
 
    s    &lt;= temp(3 downto 0);
    c_o  &lt;= temp(4);
@@ -69,7 +69,7 @@ end add_arch;</string>
           <value v="3" z="false"/>
         </entry>
       </elementAttributes>
-      <pos x="240" y="120"/>
+      <pos x="240" y="100"/>
     </visualElement>
     <visualElement>
       <elementName>In</elementName>
@@ -144,7 +144,7 @@ end loop
           </testData>
         </entry>
       </elementAttributes>
-      <pos x="260" y="240"/>
+      <pos x="300" y="40"/>
     </visualElement>
   </visualElements>
   <wires>
@@ -165,8 +165,8 @@ end loop
       <p2 x="380" y="180"/>
     </wire>
     <wire>
-      <p1 x="240" y="120"/>
-      <p2 x="260" y="120"/>
+      <p1 x="240" y="100"/>
+      <p2 x="260" y="100"/>
     </wire>
     <wire>
       <p1 x="240" y="200"/>
@@ -181,7 +181,7 @@ end loop
       <p2 x="280" y="140"/>
     </wire>
     <wire>
-      <p1 x="260" y="120"/>
+      <p1 x="260" y="100"/>
       <p2 x="260" y="140"/>
     </wire>
     <wire>