diff --git a/src/btllib/seq_reader.cpp b/src/btllib/seq_reader.cpp
index 0ed5bf14..e1f815c9 100644
--- a/src/btllib/seq_reader.cpp
+++ b/src/btllib/seq_reader.cpp
@@ -59,6 +59,8 @@ SeqReader::SeqReader(const std::string& source_path,
   check_error(short_mode() && long_mode(),
               "SeqReader: short and long mode are mutually exclusive.");
   check_error(threads == 0, "SeqReader: Number of helper threads cannot be 0.");
+  check_error(source_path.find(' ') != std::string::npos,
+              "SeqReader: filename cannot include spaces");
   start_processors();
   {
     std::unique_lock<std::mutex> lock(format_mutex);
diff --git a/src/btllib/seq_writer.cpp b/src/btllib/seq_writer.cpp
index 73dd396c..6069b4b9 100644
--- a/src/btllib/seq_writer.cpp
+++ b/src/btllib/seq_writer.cpp
@@ -16,6 +16,8 @@ SeqWriter::SeqWriter(const std::string& sink_path, Format format, bool append)
   , format(format)
   , headerchar(format == FASTA ? '>' : '@')
 {
+  check_error(sink_path.find(' ') != std::string::npos,
+              "SeqWriter: filename cannot include spaces");
 }
 
 void