diff --git a/OpenKeychain/src/main/java/org/sufficientlysecure/keychain/ui/dialog/AddSubkeyDialogFragment.java b/OpenKeychain/src/main/java/org/sufficientlysecure/keychain/ui/dialog/AddSubkeyDialogFragment.java
index d5c80d18a..450e6a5f5 100644
--- a/OpenKeychain/src/main/java/org/sufficientlysecure/keychain/ui/dialog/AddSubkeyDialogFragment.java
+++ b/OpenKeychain/src/main/java/org/sufficientlysecure/keychain/ui/dialog/AddSubkeyDialogFragment.java
@@ -33,6 +33,7 @@ import android.view.View;
 import android.view.inputmethod.InputMethodManager;
 import android.widget.AdapterView;
 import android.widget.ArrayAdapter;
+import android.widget.Button;
 import android.widget.CheckBox;
 import android.widget.CompoundButton;
 import android.widget.DatePicker;
@@ -40,6 +41,7 @@ import android.widget.EditText;
 import android.widget.Spinner;
 import android.widget.TableRow;
 import android.widget.TextView;
+import android.widget.Toast;
 
 import org.spongycastle.bcpg.PublicKeyAlgorithmTags;
 import org.spongycastle.bcpg.sig.KeyFlags;
@@ -167,60 +169,11 @@ public class AddSubkeyDialogFragment extends DialogFragment {
         mKeySizeSpinner.setSelection(1); // Default to 4096 for the key length
 
 
-        dialog.setPositiveButton(android.R.string.ok,
-                new DialogInterface.OnClickListener() {
-                    public void onClick(DialogInterface di, int id) {
-                        di.dismiss();
-                        Choice newKeyAlgorithmChoice = (Choice) mAlgorithmSpinner.getSelectedItem();
-                        int newKeySize = getProperKeyLength(newKeyAlgorithmChoice.getId(), getSelectedKeyLength());
-
-                        int flags = 0;
-                        if (mFlagCertify.isChecked()) {
-                            flags |= KeyFlags.CERTIFY_OTHER;
-                        }
-                        if (mFlagSign.isChecked()) {
-                            flags |= KeyFlags.SIGN_DATA;
-                        }
-                        if (mFlagEncrypt.isChecked()) {
-                            flags |= KeyFlags.ENCRYPT_COMMS | KeyFlags.ENCRYPT_STORAGE;
-                        }
-                        if (mFlagAuthenticate.isChecked()) {
-                            flags |= KeyFlags.AUTHENTICATION;
-                        }
-
-                        long expiry;
-                        if (mNoExpiryCheckBox.isChecked()) {
-                            expiry = 0L;
-                        } else {
-                            Calendar selectedCal = Calendar.getInstance(TimeZone.getDefault());
-                            //noinspection ResourceType
-                            selectedCal.set(mExpiryDatePicker.getYear(),
-                                    mExpiryDatePicker.getMonth(), mExpiryDatePicker.getDayOfMonth());
-                            // date picker uses default time zone, we need to convert to UTC
-                            selectedCal.setTimeZone(TimeZone.getTimeZone("UTC"));
-                            
-                            expiry = selectedCal.getTime().getTime() / 1000;
-                        }
-
-                        SaveKeyringParcel.SubkeyAdd newSubkey = new SaveKeyringParcel.SubkeyAdd(
-                                newKeyAlgorithmChoice.getId(),
-                                newKeySize,
-                                flags,
-                                expiry
-                        );
-                        mAlgorithmSelectedListener.onAlgorithmSelected(newSubkey);
-                    }
-                }
-        );
-
         dialog.setCancelable(true);
-        dialog.setNegativeButton(android.R.string.cancel,
-                new DialogInterface.OnClickListener() {
-                    public void onClick(DialogInterface di, int id) {
-                        di.dismiss();
-                    }
-                }
-        );
+
+        // onClickListener are set in onStart() to override default dismiss behaviour
+        dialog.setPositiveButton(android.R.string.ok, null);
+        dialog.setNegativeButton(android.R.string.cancel, null);
 
         final AlertDialog alertDialog = dialog.show();
 
@@ -268,6 +221,74 @@ public class AddSubkeyDialogFragment extends DialogFragment {
         return alertDialog;
     }
 
+    @Override
+    public void onStart() {
+        super.onStart();    //super.onStart() is where dialog.show() is actually called on the underlying dialog, so we have to do it after this point
+        AlertDialog d = (AlertDialog) getDialog();
+        if (d != null) {
+            Button positiveButton = d.getButton(Dialog.BUTTON_POSITIVE);
+            Button negativeButton = d.getButton(Dialog.BUTTON_NEGATIVE);
+            positiveButton.setOnClickListener(new View.OnClickListener() {
+                @Override
+                public void onClick(View v) {
+                    if (!mFlagCertify.isChecked() && !mFlagSign.isChecked()
+                            && !mFlagEncrypt.isChecked() && !mFlagAuthenticate.isChecked()) {
+                        Toast.makeText(getActivity(), R.string.edit_key_select_flag, Toast.LENGTH_LONG).show();
+                        return;
+                    }
+
+                    // dismiss only if at least one flag is selected
+                    dismiss();
+
+                    Choice newKeyAlgorithmChoice = (Choice) mAlgorithmSpinner.getSelectedItem();
+                    int newKeySize = getProperKeyLength(newKeyAlgorithmChoice.getId(), getSelectedKeyLength());
+
+                    int flags = 0;
+                    if (mFlagCertify.isChecked()) {
+                        flags |= KeyFlags.CERTIFY_OTHER;
+                    }
+                    if (mFlagSign.isChecked()) {
+                        flags |= KeyFlags.SIGN_DATA;
+                    }
+                    if (mFlagEncrypt.isChecked()) {
+                        flags |= KeyFlags.ENCRYPT_COMMS | KeyFlags.ENCRYPT_STORAGE;
+                    }
+                    if (mFlagAuthenticate.isChecked()) {
+                        flags |= KeyFlags.AUTHENTICATION;
+                    }
+
+                    long expiry;
+                    if (mNoExpiryCheckBox.isChecked()) {
+                        expiry = 0L;
+                    } else {
+                        Calendar selectedCal = Calendar.getInstance(TimeZone.getDefault());
+                        //noinspection ResourceType
+                        selectedCal.set(mExpiryDatePicker.getYear(),
+                                mExpiryDatePicker.getMonth(), mExpiryDatePicker.getDayOfMonth());
+                        // date picker uses default time zone, we need to convert to UTC
+                        selectedCal.setTimeZone(TimeZone.getTimeZone("UTC"));
+
+                        expiry = selectedCal.getTime().getTime() / 1000;
+                    }
+
+                    SaveKeyringParcel.SubkeyAdd newSubkey = new SaveKeyringParcel.SubkeyAdd(
+                            newKeyAlgorithmChoice.getId(),
+                            newKeySize,
+                            flags,
+                            expiry
+                    );
+                    mAlgorithmSelectedListener.onAlgorithmSelected(newSubkey);
+                }
+            });
+            negativeButton.setOnClickListener(new View.OnClickListener() {
+                @Override
+                public void onClick(View v) {
+                    dismiss();
+                }
+            });
+        }
+    }
+
     private int getSelectedKeyLength() {
         final String selectedItemString = (String) mKeySizeSpinner.getSelectedItem();
         final String customLengthString = getResources().getString(R.string.key_size_custom);
diff --git a/OpenKeychain/src/main/res/values/strings.xml b/OpenKeychain/src/main/res/values/strings.xml
index 51053754e..7a4f41969 100644
--- a/OpenKeychain/src/main/res/values/strings.xml
+++ b/OpenKeychain/src/main/res/values/strings.xml
@@ -457,6 +457,7 @@
         <item>Revoke Subkey</item>
     </string-array>
     <string name="edit_key_new_subkey">new</string>
+    <string name="edit_key_select_flag">Please select at least one flag!</string>
 
     <!-- Create key -->
     <string name="create_key_upload">Upload key to keyserver</string>