diff --git a/main.cpp b/main.cpp
index a6d14386..2cb71827 100644
--- a/main.cpp
+++ b/main.cpp
@@ -121,6 +121,10 @@ int main(int argc, char **argv)
             std::cout << "error: could not open file '" << filename << "'" << std::endl;
             std::exit(1);
         }
+        if (!simplecpp::isFile(filename)) {
+            std::cout << "error: could not open file '" << filename << "' - not a regular file" << std::endl;
+            std::exit(1);
+        }
         rawtokens = new simplecpp::TokenList(f, files,filename,&outputList);
     } else {
         rawtokens = new simplecpp::TokenList(filename,files,&outputList);
diff --git a/simplecpp.cpp b/simplecpp.cpp
index fd327549..8d6c9e37 100644
--- a/simplecpp.cpp
+++ b/simplecpp.cpp
@@ -42,8 +42,10 @@
 
 #ifdef _WIN32
 #  include <direct.h>
+using mode_t = unsigned short;
 #else
 #  include <sys/stat.h>
+#  include <sys/types.h>
 #endif
 
 static bool isHex(const std::string &s)
@@ -2979,9 +2981,11 @@ static std::string openHeaderDirect(std::ifstream &f, const std::string &path)
     if (nonExistingFilesCache.contains(path))
         return "";  // file is known not to exist, skip expensive file open call
 #endif
-    f.open(path.c_str());
-    if (f.is_open())
-        return path;
+    if (simplecpp::isFile(path)) {
+        f.open(path.c_str());
+        if (f.is_open())
+            return path;
+    }
 #ifdef SIMPLECPP_WINDOWS
     nonExistingFilesCache.add(path);
 #endif
@@ -3102,6 +3106,9 @@ bool simplecpp::FileDataCache::getFileId(const std::string &path, FileID &id)
     if (stat(path.c_str(), &statbuf) != 0)
         return false;
 
+    if ((statbuf.st_mode & S_IFMT) != S_IFREG)
+        return false;
+
     id.dev = statbuf.st_dev;
     id.ino = statbuf.st_ino;
 
@@ -3838,3 +3845,21 @@ std::string simplecpp::getCppStdString(const std::string &std)
 {
     return getCppStdString(getCppStd(std));
 }
+
+static mode_t file_type(const std::string &path)
+{
+    struct stat file_stat;
+    if (stat(path.c_str(), &file_stat) == -1)
+        return 0;
+    return file_stat.st_mode & S_IFMT;
+}
+
+bool simplecpp::isFile(const std::string &path)
+{
+    return file_type(path) == S_IFREG;
+}
+
+bool simplecpp::isDirectory(const std::string &path)
+{
+    return file_type(path) == S_IFDIR;
+}
diff --git a/simplecpp.h b/simplecpp.h
index 8268fa8d..1efdc96e 100644
--- a/simplecpp.h
+++ b/simplecpp.h
@@ -353,6 +353,20 @@ namespace simplecpp {
         bool removeComments; /** remove comment tokens from included files */
     };
 
+    /**
+     * @brief Checks if given path is a file
+     * @param path Path to be checked
+     * @return true if given path is a file
+     */
+    SIMPLECPP_LIB bool isFile(const std::string &path);
+
+    /**
+     * @brief Checks if a given path is a directory
+     * @param path Path to be checked
+     * @return true if given path is a directory
+     */
+    SIMPLECPP_LIB bool isDirectory(const std::string &path);
+
     struct SIMPLECPP_LIB FileData {
         /** The canonical filename associated with this data */
         std::string filename;
diff --git a/test.cpp b/test.cpp
index ccb653ca..bc321fc9 100644
--- a/test.cpp
+++ b/test.cpp
@@ -2053,6 +2053,44 @@ static void missingHeader4()
     ASSERT_EQUALS("file0,1,syntax_error,No header in #include\n", toString(outputList));
 }
 
+#ifndef _WIN32
+static void missingHeader5()
+{
+    // this is a directory
+    const char code[] = "#include \"/\"\n";
+    simplecpp::OutputList outputList;
+    ASSERT_EQUALS("", preprocess(code, &outputList));
+    ASSERT_EQUALS("file0,1,missing_header,Header not found: \"/\"\n", toString(outputList));
+}
+
+static void missingHeader6()
+{
+    // this is a directory
+    const char code[] = "#include \"/usr\"\n";
+    simplecpp::OutputList outputList;
+    ASSERT_EQUALS("", preprocess(code, &outputList));
+    ASSERT_EQUALS("file0,1,missing_header,Header not found: \"/usr\"\n", toString(outputList));
+}
+
+static void missingHeader7()
+{
+    // this is a directory
+    const char code[] = "#include </>\n";
+    simplecpp::OutputList outputList;
+    ASSERT_EQUALS("", preprocess(code, &outputList));
+    ASSERT_EQUALS("file0,1,missing_header,Header not found: </>\n", toString(outputList));
+}
+
+static void missingHeader8()
+{
+    // this is a directory
+    const char code[] = "#include </usr>\n";
+    simplecpp::OutputList outputList;
+    ASSERT_EQUALS("", preprocess(code, &outputList));
+    ASSERT_EQUALS("file0,1,missing_header,Header not found: </usr>\n", toString(outputList));
+}
+#endif
+
 static void nestedInclude()
 {
     const char code[] = "#include \"test.h\"\n";
@@ -3183,6 +3221,16 @@ static void fuzz_crash()
     }
 }
 
+static void leak()
+{
+    const char code[] = "#include</\\\\>\n"
+                        "#include</\\\\>\n";
+    simplecpp::OutputList outputList;
+    ASSERT_EQUALS("", preprocess(code, &outputList));
+    ASSERT_EQUALS("file0,1,missing_header,Header not found: </\\\\>\n"
+                  "file0,2,missing_header,Header not found: </\\\\>\n", toString(outputList));
+}
+
 int main(int argc, char **argv)
 {
     TEST_CASE(backslash);
@@ -3356,6 +3404,12 @@ int main(int argc, char **argv)
     TEST_CASE(missingHeader2);
     TEST_CASE(missingHeader3);
     TEST_CASE(missingHeader4);
+#ifndef _WIN32
+    TEST_CASE(missingHeader5);
+    TEST_CASE(missingHeader6);
+    TEST_CASE(missingHeader7);
+    TEST_CASE(missingHeader8);
+#endif
     TEST_CASE(nestedInclude);
     TEST_CASE(systemInclude);
     TEST_CASE(circularInclude);
@@ -3437,5 +3491,7 @@ int main(int argc, char **argv)
 
     TEST_CASE(fuzz_crash);
 
+    TEST_CASE(leak);
+
     return numberOfFailedAssertions > 0 ? EXIT_FAILURE : EXIT_SUCCESS;
 }