diff --git a/simplecpp.cpp b/simplecpp.cpp
index 320836be..08c3a503 100644
--- a/simplecpp.cpp
+++ b/simplecpp.cpp
@@ -2438,21 +2438,26 @@ namespace simplecpp {
         return windowsPath;
     }
 #endif
-}
 
+    bool isAbsolutePath(const std::string &path)
+    {
 #ifdef SIMPLECPP_WINDOWS
-static bool isAbsolutePath(const std::string &path)
-{
-    if (path.length() >= 3 && path[0] > 0 && std::isalpha(path[0]) && path[1] == ':' && (path[2] == '\\' || path[2] == '/'))
-        return true;
-    return path.length() > 1U && (path[0] == '/' || path[0] == '\\');
-}
+        // C:\\path\\file
+        // C:/path/file
+        if (path.length() >= 3 && std::isalpha(path[0]) && path[1] == ':' && (path[2] == '\\' || path[2] == '/'))
+            return true;
+
+        // \\host\path\file
+        // //host/path/file
+        if (path.length() >= 2 && (path[0] == '\\' || path[0] == '/') && (path[1] == '\\' || path[1] == '/'))
+            return true;
+
+        return false;
 #else
-static bool isAbsolutePath(const std::string &path)
-{
-    return path.length() > 1U && path[0] == '/';
-}
+        return !path.empty() && path[0] == '/';
 #endif
+    }
+}
 
 namespace simplecpp {
     /**
@@ -3013,7 +3018,7 @@ static std::string openHeaderDirect(std::ifstream &f, const std::string &path)
 
 static std::string openHeader(std::ifstream &f, const simplecpp::DUI &dui, const std::string &sourcefile, const std::string &header, bool systemheader)
 {
-    if (isAbsolutePath(header))
+    if (simplecpp::isAbsolutePath(header))
         return openHeaderDirect(f, simplecpp::simplifyPath(header));
 
     // prefer first to search the header relatively to source file if found, when not a system header
diff --git a/simplecpp.h b/simplecpp.h
index c6c3b515..b461de47 100644
--- a/simplecpp.h
+++ b/simplecpp.h
@@ -556,6 +556,9 @@ namespace simplecpp {
     /** Returns the __cplusplus value for a given standard */
     SIMPLECPP_LIB std::string getCppStdString(const std::string &std);
     SIMPLECPP_LIB std::string getCppStdString(cppstd_t std);
+
+    /** Checks if given path is absolute */
+    SIMPLECPP_LIB bool isAbsolutePath(const std::string &path);
 }
 
 #undef SIMPLECPP_TOKENLIST_ALLOW_PTR
diff --git a/test.cpp b/test.cpp
index b9869b5b..2f56ae9b 100644
--- a/test.cpp
+++ b/test.cpp
@@ -45,7 +45,7 @@ static int assertEquals(const std::string &expected, const std::string &actual,
     if (expected != actual) {
         numberOfFailedAssertions++;
         std::cerr << "------ assertion failed ---------" << std::endl;
-        std::cerr << "line " << line << std::endl;
+        std::cerr << "line test.cpp:" << line << std::endl;
         std::cerr << "expected:" << pprint(expected) << std::endl;
         std::cerr << "actual:" << pprint(actual) << std::endl;
     }
@@ -3246,6 +3246,39 @@ static void safe_api()
 #endif
 }
 
+static void isAbsolutePath() {
+#ifdef _WIN32
+    ASSERT_EQUALS(true, simplecpp::isAbsolutePath("C:\\foo\\bar"));
+    ASSERT_EQUALS(true, simplecpp::isAbsolutePath("C:/foo/bar"));
+    ASSERT_EQUALS(true, simplecpp::isAbsolutePath("\\\\foo\\bar"));
+
+    ASSERT_EQUALS(false, simplecpp::isAbsolutePath("foo\\bar"));
+    ASSERT_EQUALS(false, simplecpp::isAbsolutePath("foo/bar"));
+    ASSERT_EQUALS(false, simplecpp::isAbsolutePath("foo.cpp"));
+    ASSERT_EQUALS(false, simplecpp::isAbsolutePath("C:foo.cpp"));
+    ASSERT_EQUALS(false, simplecpp::isAbsolutePath("C:foo\\bar.cpp"));
+    ASSERT_EQUALS(false, simplecpp::isAbsolutePath("bar.cpp"));
+    //ASSERT_EQUALS(true, simplecpp::isAbsolutePath("\\")); // TODO
+    ASSERT_EQUALS(false, simplecpp::isAbsolutePath("0:\\foo\\bar"));
+    ASSERT_EQUALS(false, simplecpp::isAbsolutePath("0:/foo/bar"));
+    ASSERT_EQUALS(false, simplecpp::isAbsolutePath("\\foo\\bar"));
+    //ASSERT_EQUALS(false, simplecpp::isAbsolutePath("\\\\")); // TODO
+    //ASSERT_EQUALS(false, simplecpp::isAbsolutePath("//")); // TODO
+    ASSERT_EQUALS(false, simplecpp::isAbsolutePath("/foo/bar"));
+    ASSERT_EQUALS(false, simplecpp::isAbsolutePath("/"));
+#else
+    ASSERT_EQUALS(true, simplecpp::isAbsolutePath("/foo/bar"));
+    ASSERT_EQUALS(true, simplecpp::isAbsolutePath("/"));
+    ASSERT_EQUALS(true, simplecpp::isAbsolutePath("//host/foo/bar"));
+
+    ASSERT_EQUALS(false, simplecpp::isAbsolutePath("foo/bar"));
+    ASSERT_EQUALS(false, simplecpp::isAbsolutePath("foo.cpp"));
+    ASSERT_EQUALS(false, simplecpp::isAbsolutePath("C:\\foo\\bar"));
+    ASSERT_EQUALS(false, simplecpp::isAbsolutePath("C:/foo/bar"));
+    ASSERT_EQUALS(false, simplecpp::isAbsolutePath("\\\\foo\\bar"));
+#endif
+}
+
 // crashes detected by fuzzer
 static void fuzz_crash()
 {
@@ -3525,6 +3558,8 @@ int main(int argc, char **argv)
 
     TEST_CASE(safe_api);
 
+    TEST_CASE(isAbsolutePath);
+
     TEST_CASE(fuzz_crash);
 
     TEST_CASE(leak);