diff --git a/src/Buffer.cpp b/src/Buffer.cpp
index c4ce8ea053..9ec20e0fbb 100644
--- a/src/Buffer.cpp
+++ b/src/Buffer.cpp
@@ -2446,15 +2446,16 @@ void Buffer::reloadBibInfoCache() const
 		return;
 
 	d->bibinfo_.clear();
-	collectBibKeys();
+	FileNameList checkedFiles;
+	collectBibKeys(checkedFiles);
 	d->bibinfo_cache_valid_ = true;
 }
 
 
-void Buffer::collectBibKeys() const
+void Buffer::collectBibKeys(FileNameList & checkedFiles) const
 {
 	for (InsetIterator it = inset_iterator_begin(inset()); it; ++it)
-		it->collectBibKeys(it);
+		it->collectBibKeys(it, checkedFiles);
 }
 
 
diff --git a/src/Buffer.h b/src/Buffer.h
index 165f5d8795..35e7632973 100644
--- a/src/Buffer.h
+++ b/src/Buffer.h
@@ -17,6 +17,7 @@
 #include "support/unique_ptr.h"
 #include "support/strfwd.h"
 #include "support/types.h"
+#include "support/FileNameList.h"
 
 #include <map>
 #include <list>
@@ -520,7 +521,7 @@ public:
 	/// or just for it, if it isn't a child.
 	BiblioInfo const & masterBibInfo() const;
 	/// collect bibliography info from the various insets in this buffer.
-	void collectBibKeys() const;
+	void collectBibKeys(support::FileNameList &) const;
 	/// add some BiblioInfo to our cache
 	void addBiblioInfo(BiblioInfo const & bi) const;
 	/// add a single piece of bibliography info to our cache
diff --git a/src/insets/Inset.h b/src/insets/Inset.h
index 578a7f4d5a..94e9d1a668 100644
--- a/src/insets/Inset.h
+++ b/src/insets/Inset.h
@@ -23,6 +23,7 @@
 
 #include "support/strfwd.h"
 #include "support/types.h"
+#include "support/FileNameList.h"
 
 #include <climits>
 
@@ -529,7 +530,7 @@ public:
 	                      UpdateType /* utype*/,
 	                      TocBackend & /* tocbackend */) const {}
 	/// Collect BibTeX information
-	virtual void collectBibKeys(InsetIterator const &) const {}
+	virtual void collectBibKeys(InsetIterator const &, support::FileNameList &) const {}
 	/// Update the counters of this inset and of its contents.
 	/// The boolean indicates whether we are preparing for output, e.g.,
 	/// of XHTML.
diff --git a/src/insets/InsetBibitem.cpp b/src/insets/InsetBibitem.cpp
index afc30ae37d..d5ebaf7640 100644
--- a/src/insets/InsetBibitem.cpp
+++ b/src/insets/InsetBibitem.cpp
@@ -285,7 +285,7 @@ docstring bibitemWidest(Buffer const & buffer, OutputParams const & runparams)
 }
 
 
-void InsetBibitem::collectBibKeys(InsetIterator const & it) const
+void InsetBibitem::collectBibKeys(InsetIterator const & it, FileNameList & /*checkedFiles*/) const
 {
 	docstring const key = getParam("key");
 	docstring const label = getParam("label");
diff --git a/src/insets/InsetBibitem.h b/src/insets/InsetBibitem.h
index 41497e1849..ba33732ad0 100644
--- a/src/insets/InsetBibitem.h
+++ b/src/insets/InsetBibitem.h
@@ -60,7 +60,7 @@ public:
 	///
 	docstring xhtml(XHTMLStream &, OutputParams const &) const;
 	///
-	void collectBibKeys(InsetIterator const &) const;
+	void collectBibKeys(InsetIterator const &, support::FileNameList &) const;
 	/// update the counter of this inset
 	void updateBuffer(ParIterator const &, UpdateType);
 	///@}
diff --git a/src/insets/InsetBibtex.cpp b/src/insets/InsetBibtex.cpp
index a905110773..30b169acb0 100644
--- a/src/insets/InsetBibtex.cpp
+++ b/src/insets/InsetBibtex.cpp
@@ -645,13 +645,13 @@ namespace {
 } // namespace
 
 
-void InsetBibtex::collectBibKeys(InsetIterator const & /*di*/) const
+void InsetBibtex::collectBibKeys(InsetIterator const & /*di*/, FileNameList & checkedFiles) const
 {
-	parseBibTeXFiles();
+	parseBibTeXFiles(checkedFiles);
 }
 
 
-void InsetBibtex::parseBibTeXFiles() const
+void InsetBibtex::parseBibTeXFiles(FileNameList & checkedFiles) const
 {
 	// This bibtex parser is a first step to parse bibtex files
 	// more precisely.
@@ -678,7 +678,14 @@ void InsetBibtex::parseBibTeXFiles() const
 	support::FileNamePairList::const_iterator it = files.begin();
 	support::FileNamePairList::const_iterator en = files.end();
 	for (; it != en; ++ it) {
-		ifdocstream ifs(it->second.toFilesystemEncoding().c_str(),
+		FileName const bibfile = it->second;
+		if (find(checkedFiles.begin(), checkedFiles.end(), bibfile) != checkedFiles.end())
+			// already checked this one. Skip.
+			continue;
+		else
+			// record that we check this.
+			checkedFiles.push_back(bibfile);
+		ifdocstream ifs(bibfile.toFilesystemEncoding().c_str(),
 			ios_base::in, buffer().masterParams().encoding().iconvName());
 
 		char_type ch;
diff --git a/src/insets/InsetBibtex.h b/src/insets/InsetBibtex.h
index 3ba96a29e8..2d033464f0 100644
--- a/src/insets/InsetBibtex.h
+++ b/src/insets/InsetBibtex.h
@@ -57,7 +57,7 @@ public:
 	int plaintext(odocstringstream & ods, OutputParams const & op,
 	              size_t max_length = INT_MAX) const;
 	///
-	void collectBibKeys(InsetIterator const &) const;
+	void collectBibKeys(InsetIterator const &, support::FileNameList &) const;
 	///
 	void validate(LaTeXFeatures &) const;
 	///
@@ -84,7 +84,7 @@ private:
 	///
 	void editDatabases() const;
 	///
-	void parseBibTeXFiles() const;
+	void parseBibTeXFiles(support::FileNameList &) const;
 	///
 	bool usingBiblatex() const;
 
diff --git a/src/insets/InsetInclude.cpp b/src/insets/InsetInclude.cpp
index 6af715fb22..d6e3ae2c63 100644
--- a/src/insets/InsetInclude.cpp
+++ b/src/insets/InsetInclude.cpp
@@ -1072,7 +1072,7 @@ void InsetInclude::validate(LaTeXFeatures & features) const
 }
 
 
-void InsetInclude::collectBibKeys(InsetIterator const & /*di*/) const
+void InsetInclude::collectBibKeys(InsetIterator const & /*di*/, FileNameList & checkedFiles) const
 {
 	Buffer * child = loadIfNeeded();
 	if (!child)
@@ -1082,7 +1082,7 @@ void InsetInclude::collectBibKeys(InsetIterator const & /*di*/) const
 	// But it'll have to do for now.
 	if (child == &buffer())
 		return;
-	child->collectBibKeys();
+	child->collectBibKeys(checkedFiles);
 }
 
 
diff --git a/src/insets/InsetInclude.h b/src/insets/InsetInclude.h
index 7be5f7892d..009b49e3ac 100644
--- a/src/insets/InsetInclude.h
+++ b/src/insets/InsetInclude.h
@@ -92,7 +92,7 @@ public:
 	 *  \param keys the list of bibkeys in the child buffer.
 	 *  \param it not used here
 	 */
-	void collectBibKeys(InsetIterator const &) const;
+	void collectBibKeys(InsetIterator const &, support::FileNameList &) const;
 	///
 	bool hasSettings() const { return true; }
 	///