diff --git a/lib/mathlib.cpp b/lib/mathlib.cpp
index 7ed5b8830..fbdf0dbc2 100644
--- a/lib/mathlib.cpp
+++ b/lib/mathlib.cpp
@@ -346,6 +346,10 @@ static unsigned int encodeMultiChar(const std::string& str)
     return retval;
 }
 
+static bool isoctal(int c) {
+    return c>='0' && c<='7';
+}
+
 MathLib::bigint MathLib::characterLiteralToLongNumber(const std::string& str)
 {
     if (str.empty())
@@ -356,6 +360,11 @@ MathLib::bigint MathLib::characterLiteralToLongNumber(const std::string& str)
         return std::strtoul(str.substr(2).c_str(), NULL, 16);
     }
 
+    // '\123'
+    if (str.size() == 4 && str[0] == '\\' && isoctal(str[1]) && isoctal(str[2]) && isoctal(str[3])) {
+        return (char)std::strtoul(str.substr(1).c_str(), NULL, 8);
+    }
+
     // C99 6.4.4.4
     // The value of an integer character constant containing more than one character (e.g., 'ab'),
     // or containing a character or escape sequence that does not map to a single-byte execution character,
diff --git a/test/testmathlib.cpp b/test/testmathlib.cpp
index ecdf5eec2..82d80d428 100644
--- a/test/testmathlib.cpp
+++ b/test/testmathlib.cpp
@@ -275,6 +275,9 @@ private:
 
         // from char
         ASSERT_EQUALS((int)('A'),    MathLib::toLongNumber("'A'"));
+        ASSERT_EQUALS((int)('\x10'), MathLib::toLongNumber("'\\x10'"));
+        ASSERT_EQUALS((int)('\100'), MathLib::toLongNumber("'\\100'"));
+        ASSERT_EQUALS((int)('\200'), MathLib::toLongNumber("'\\200'"));
 #ifdef __GNUC__
         // BEGIN Implementation-specific results
         ASSERT_EQUALS((int)('AB'),    MathLib::toLongNumber("'AB'"));