diff --git a/src/Buffer.cpp b/src/Buffer.cpp
index 2c18655..b0db5c7 100644
--- a/src/Buffer.cpp
+++ b/src/Buffer.cpp
@@ -1922,7 +1922,11 @@ int Buffer::runChktex()
 
 void Buffer::validate(LaTeXFeatures & features) const
 {
-	params().validate(features);
+	// Validate the buffer params, but not for included
+	// files, since they also use the parent buffer's
+	// params (# 5941)
+	if (!features.runparams().is_child)
+		params().validate(features);
 
 	for_each(paragraphs().begin(), paragraphs().end(),
 		 bind(&Paragraph::validate, _1, ref(features)));
diff --git a/src/insets/InsetInclude.cpp b/src/insets/InsetInclude.cpp
index 2a6f92b..e846763 100644
--- a/src/insets/InsetInclude.cpp
+++ b/src/insets/InsetInclude.cpp
@@ -934,7 +934,9 @@ void InsetInclude::validate(LaTeXFeatures & features) const
 			// otherwise it would always be the master buffer,
 			// and nested includes would not work.
 			features.setBuffer(*tmp);
+			features.runparams().is_child = true;
 			tmp->validate(features);
+			features.runparams().is_child =false;
 			features.setBuffer(buffer());
 		}
 	}