diff --git a/src/frontends/qt4/GuiDocument.cpp b/src/frontends/qt4/GuiDocument.cpp
index 8469447f60..9d45890e9d 100644
--- a/src/frontends/qt4/GuiDocument.cpp
+++ b/src/frontends/qt4/GuiDocument.cpp
@@ -726,6 +726,8 @@ GuiDocument::GuiDocument(GuiView & lv)
 
 	connect(textLayoutModule->MathIndentCB, SIGNAL(toggled(bool)),
 		this, SLOT(change_adaptor()));
+	connect(textLayoutModule->MathIndentCB, SIGNAL(toggled(bool)),
+		this, SLOT(allowMathIndent()));
 	connect(textLayoutModule->MathIndentCO, SIGNAL(activated(int)),
 		this, SLOT(change_adaptor()));
 	connect(textLayoutModule->MathIndentCO, SIGNAL(activated(int)),
@@ -1609,6 +1611,20 @@ void GuiDocument::enableSkip(bool skip)
 		setSkip(textLayoutModule->skipCO->currentIndex());
 }
 
+void GuiDocument::allowMathIndent() {
+	// only disable when not checked, checked does not always allow enabling
+	if (!textLayoutModule->MathIndentCB->isChecked()) {
+		textLayoutModule->MathIndentLE->setEnabled(false);
+		textLayoutModule->MathIndentLengthCO->setEnabled(false);
+	}
+	if (textLayoutModule->MathIndentCB->isChecked()
+	    && textLayoutModule->MathIndentCO->currentIndex() == 1) {
+			textLayoutModule->MathIndentLE->setEnabled(true);
+			textLayoutModule->MathIndentLengthCO->setEnabled(true);
+	}
+	isValid();
+}
+
 void GuiDocument::setMathIndent(int item)
 {
 	bool const enable = (item == 1);
diff --git a/src/frontends/qt4/GuiDocument.h b/src/frontends/qt4/GuiDocument.h
index b33fca95f8..7527a59edc 100644
--- a/src/frontends/qt4/GuiDocument.h
+++ b/src/frontends/qt4/GuiDocument.h
@@ -109,6 +109,7 @@ private Q_SLOTS:
 	void enableIndent(bool);
 	void setSkip(int);
 	void enableSkip(bool);
+	void allowMathIndent();
 	void setMathIndent(int);
 	void browseLayout();
 	void browseMaster();