diff --git a/src/toolbars/SpectralSelectionBar.cpp b/src/toolbars/SpectralSelectionBar.cpp
index fb443452c..e167c55ca 100644
--- a/src/toolbars/SpectralSelectionBar.cpp
+++ b/src/toolbars/SpectralSelectionBar.cpp
@@ -146,12 +146,14 @@ void SpectralSelectionBar::Populate()
 
    mCenterCtrl = new NumericTextCtrl(
       NumericConverter::FREQUENCY, this, OnCenterID, frequencyFormatName, 0.0);
+   mCenterCtrl->SetInvalidValue(SelectedRegion::UndefinedFrequency);
    mCenterCtrl->SetName(_("Center Frequency:"));
    mCenterCtrl->EnableMenu();
    subSizer->Add(mCenterCtrl, 0, wxALIGN_CENTER_VERTICAL | wxRIGHT, 5);
 
    mWidthCtrl = new NumericTextCtrl(
       NumericConverter::BANDWIDTH, this, OnWidthID, bandwidthFormatName, 0.0);
+   mWidthCtrl->SetInvalidValue(-1.0);
    mWidthCtrl->SetName(wxString(_("Bandwidth:")));
    mWidthCtrl->EnableMenu();
    subSizer->Add(mWidthCtrl, 0, wxALIGN_CENTER_VERTICAL | wxRIGHT, 0);
@@ -228,7 +230,11 @@ void SpectralSelectionBar::ModifySpectralSelection(bool done)
    if (mbCenterAndWidth) {
       mCenter = mCenterCtrl->GetValue();
       mWidth = mWidthCtrl->GetValue();
-      if (mCenter < 0 && mWidth < 0)
+      if ((mCenter < 0 || mWidth < 0) &&
+          (mLow >= 0 || mHigh >= 0))
+         // Transition from defined spectral selection to undefined
+         bottom = top = SelectedRegion::UndefinedFrequency;
+      else if (mCenter < 0 && mWidth < 0)
          bottom = top = SelectedRegion::UndefinedFrequency;
       else {
          if (mCenter < 0) {
diff --git a/src/widgets/NumericTextCtrl.cpp b/src/widgets/NumericTextCtrl.cpp
index 181528e7a..9674345cd 100644
--- a/src/widgets/NumericTextCtrl.cpp
+++ b/src/widgets/NumericTextCtrl.cpp
@@ -1612,7 +1612,7 @@ void NumericTextCtrl::OnCaptureKey(wxCommandEvent &event)
       case WXK_TAB:
       case WXK_RETURN:
       case WXK_NUMPAD_ENTER:
-      case '-':
+      case WXK_DELETE:
          return;
 
       default:
@@ -1635,7 +1635,7 @@ void NumericTextCtrl::OnKeyUp(wxKeyEvent &event)
       keyCode -= WXK_NUMPAD0 - '0';
 
    if ((keyCode >= '0' && keyCode <= '9') ||
-       (keyCode == '-') ||
+       (keyCode == WXK_DELETE) ||
        (keyCode == WXK_BACK) ||
        (keyCode == WXK_UP) ||
        (keyCode == WXK_DOWN)) {
@@ -1680,7 +1680,7 @@ void NumericTextCtrl::OnKeyDown(wxKeyEvent &event)
       Updated();
    }
 
-   else if (!mReadOnly && keyCode == '-') {
+   else if (!mReadOnly && keyCode == WXK_DELETE) {
       if (mAllowInvalidValue)
          SetValue(mInvalidValue);
    }