diff --git a/src/tengfilesystem.cc b/src/tengfilesystem.cc
index 1f4a802..de65057 100644
--- a/src/tengfilesystem.cc
+++ b/src/tengfilesystem.cc
@@ -38,7 +38,7 @@ std::string Filesystem_t::read(const std::string& filename_) const
     tengNormalizeFilename(filename);
 
     FILE* fp = fopen(filename.c_str(), "rb");
-    if (fp == 0) throw std::runtime_error("fopen(" + filename + ")");
+    if (fp == 0) throw std::runtime_error("Cannot open input file '" + filename + "'");
 
     char buf[1024];
     int i;
diff --git a/src/tenglex1.cc b/src/tenglex1.cc
index a558b06..6ad41ba 100644
--- a/src/tenglex1.cc
+++ b/src/tenglex1.cc
@@ -55,16 +55,18 @@ Lex1_t::Lex1_t(const std::string &input, const std::string &fname)
 /** Initialize lexical analyzer from file.
   * @param filesystem Filesystem to use.
   * @param input Input file to read. */
-Lex1_t::Lex1_t(const FilesystemInterface_t *filesystem,
-        const std::string &fname,
-        const Error_t::Position_t &position,
-        Error_t &error)
-try
-    : input(filesystem->read(fname)), position(0), filename(fname), line(1), column(0)
+Lex1_t::Lex1_t(const FilesystemInterface_t* filesystem,
+               const std::string& fname,
+               const Error_t::Position_t& position,
+               Error_t& error)
+    : position(0), filename(fname), line(1), column(0)
 {
-}
-catch (const std::exception &e) {
-    error.logSyscallError(Error_t::LL_ERROR, position, e.what());
+    try {
+        input = filesystem->read(fname);
+    }
+    catch (const std::exception& e) {
+        error.logSyscallError(Error_t::LL_ERROR, position, e.what());
+    }
 }