diff --git a/src/frontends/qt4/GuiTabular.cpp b/src/frontends/qt4/GuiTabular.cpp
index a1f01c4d73..8ec1164148 100644
--- a/src/frontends/qt4/GuiTabular.cpp
+++ b/src/frontends/qt4/GuiTabular.cpp
@@ -176,6 +176,8 @@ void GuiTabular::checkEnabled()
 	interlinespaceED->setEnabled(interlinespaceCO->currentIndex() == 2);
 	interlinespaceUnit->setEnabled(interlinespaceCO->currentIndex() == 2);
 
+	// setting as longtable is not allowed when table is inside a float
+	longTabularCB->setEnabled(funcEnabled(Tabular::SET_LONGTABULAR));
 	bool const longtabular = longTabularCB->isChecked();
 	longtableGB->setEnabled(true);
 	newpageCB->setEnabled(longtabular);
diff --git a/src/insets/InsetTabular.cpp b/src/insets/InsetTabular.cpp
index 00a155d918..ffbe4f96a5 100644
--- a/src/insets/InsetTabular.cpp
+++ b/src/insets/InsetTabular.cpp
@@ -4313,6 +4313,9 @@ bool InsetTabular::getStatus(Cursor & cur, FuncRequest const & cmd,
 			break;
 
 		case Tabular::SET_LONGTABULAR:
+			// setting as longtable is not allowed when table is inside a float
+			if (cur.innerInsetOfType(FLOAT_CODE) != 0)
+				status.setEnabled(false);
 			status.setOnOff(tabular.is_long_tabular);
 			break;