diff --git a/.bumpversion.cfg b/.bumpversion.cfg
index cb38708..6d87aed 100644
--- a/.bumpversion.cfg
+++ b/.bumpversion.cfg
@@ -1,8 +1,9 @@
 [bumpversion]
-current_version = 3.0.3
+current_version = 3.0.4
 commit = True
 tag = False
 
 [bumpversion:file:cqc/__init__.py]
+
 [bumpversion:file:README.md]
 
diff --git a/CHANGELOG.md b/CHANGELOG.md
index e4b74a1..9bad870 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -6,6 +6,10 @@ For more details refer to the [documentation](https://softwarequtech.github.io/S
 Upcoming
 --------
 
+2019-10-16 (v3.0.4)
+-------------------
+- If a CQCConnection does not manage to connect to the cqc server, the used app ID is popped from the list of used ones, to be reused again.
+
 2019-10-08 (v3.0.3)
 -------------------
 - Fixed bug that mixes up return messages for different application IDs
diff --git a/README.md b/README.md
index 3da3bc9..059cc0a 100644
--- a/README.md
+++ b/README.md
@@ -1,4 +1,4 @@
-# CQC (3.0.3)
+# CQC (3.0.4)
 
 The classical-quantum combiner (CQC) interface is an interface between higher layers and hardware in a Quantum Internet. It comes with a Python, C and Rust library for constructing CQC messages. The Python library is definitely the best place to get started.
 
diff --git a/cqc/__init__.py b/cqc/__init__.py
index d298347..9a8a1b1 100644
--- a/cqc/__init__.py
+++ b/cqc/__init__.py
@@ -1 +1 @@
-__version__ = '3.0.3'
+__version__ = '3.0.4'
diff --git a/cqc/pythonLib.py b/cqc/pythonLib.py
index df28c85..2216960 100644
--- a/cqc/pythonLib.py
+++ b/cqc/pythonLib.py
@@ -243,7 +243,7 @@ def __init__(self, name, socket_address=None, appID=None, pend_messages=False,
             self._appID = appID
             self._appIDs[name].append(self._appID)
 
-            # Buffer received data
+        # Buffer received data
         self.buf = None
 
         # ClassicalServer
@@ -302,6 +302,7 @@ def __init__(self, name, socket_address=None, appID=None, pend_messages=False,
                 time.sleep(self._conn_retry_time)
                 self._s.close()
                 if not retry_connection:
+                    self.close(release_qubits=False)
                     raise err
             except Exception as err:
                 logging.warning("App {} : Critical error when connection to CQC server: {}".format(self.name, err))
@@ -349,21 +350,27 @@ def get_appID(self):
 
     def close(self, release_qubits=True):
         """
-        Closes the connection. Releases all qubits
+        Closes the connection. Releases all qubits and remove the app ID from the used app IDs.
         """
         if release_qubits:
             self.release_all_qubits()
         self._s.close()
-        try:
-            self._appIDs[self.name].remove(self._appID)
-        except ValueError:
-            pass  # Already closed
+        self._pop_app_id()
 
         self.closeClassicalServer()
 
         for name in list(self._classicalConn):
             self.closeClassicalChannel(name)
 
+    def _pop_app_id(self):
+        """
+        Removes the used appID from the list.
+        """
+        try:
+            self._appIDs[self.name].remove(self._appID)
+        except ValueError:
+            pass  # Already removed
+
     def startClassicalServer(self):
         """
         Sets up a server for the application communication, if not already set up.