diff --git a/lib/mathlib.cpp b/lib/mathlib.cpp
index 2c67426ff..496260711 100644
--- a/lib/mathlib.cpp
+++ b/lib/mathlib.cpp
@@ -235,7 +235,10 @@ std::string MathLib::subtract(const std::string &first, const std::string &secon
 std::string MathLib::divide(const std::string &first, const std::string &second)
 {
     if (MathLib::isInt(first) && MathLib::isInt(second)) {
-        return toString<bigint>(toLongNumber(first) / toLongNumber(second));
+        bigint b = toLongNumber(second);
+        if (b == 0)
+            throw InternalError(0, "Internal Error: Division by zero");
+        return toString<bigint>(toLongNumber(first) / b);
     }
     return toString<double>(toDoubleNumber(first) / toDoubleNumber(second));
 }
@@ -251,7 +254,10 @@ std::string MathLib::multiply(const std::string &first, const std::string &secon
 std::string MathLib::mod(const std::string &first, const std::string &second)
 {
     if (MathLib::isInt(first) && MathLib::isInt(second)) {
-        return toString<MathLib::bigint>(toLongNumber(first) % toLongNumber(second));
+        bigint b = toLongNumber(second);
+        if (b == 0)
+            throw InternalError(0, "Internal Error: Division by zero");
+        return toString<MathLib::bigint>(toLongNumber(first) % b);
     }
     return toString<double>(fmod(toDoubleNumber(first),toDoubleNumber(second)));
 }
diff --git a/test/testmathlib.cpp b/test/testmathlib.cpp
index 2837fb7cc..6e31d45b6 100644
--- a/test/testmathlib.cpp
+++ b/test/testmathlib.cpp
@@ -100,6 +100,7 @@ private:
         ASSERT_EQUALS("0"  , MathLib::subtract("0", "0."));
         ASSERT_EQUALS("0.99999999"  , MathLib::subtract("1", "0.00000001")); // #4016
         ASSERT_EQUALS("30666.22"  , MathLib::subtract("30666.22", "0.0"));  // #4068
+        ASSERT_EQUALS("0.0" , MathLib::subtract("0.0", "0.0"));
 
         // multiply
         ASSERT_EQUALS("-0.003"          , MathLib::multiply("-1e-3", "3"));
@@ -123,20 +124,23 @@ private:
         ASSERT_EQUALS("5"   , MathLib::divide("25.5", "5.1"));
         ASSERT_EQUALS("7"   , MathLib::divide("21.", "3"));
         ASSERT_EQUALS("1"   , MathLib::divide("3", "2"));
-        ASSERT_EQUALS("0.0" , MathLib::subtract("0.0", "0.0"));
+        ASSERT_THROW(MathLib::divide("123", "0"), InternalError); // throw
+        MathLib::divide("123", "0.0"); // don't throw
 
         // Unknown action should throw exception
         ASSERT_THROW(MathLib::calculate("1","2",'j'),InternalError);
     }
 
     void calculate1() const { // mod
-        ASSERT_EQUALS("0"    , MathLib::calculate("2"	 , "1"    , '%'));
+        ASSERT_EQUALS("0"    , MathLib::calculate("2"    , "1"    , '%'));
         ASSERT_EQUALS("0"    , MathLib::calculate("2.0"  , "1.0"  , '%'));
         ASSERT_EQUALS("2"    , MathLib::calculate("12"   , "5"   , '%'));
         ASSERT_EQUALS("1"    , MathLib::calculate("100"  , "3"   , '%'));
         ASSERT_EQUALS("12"   , MathLib::calculate("12.0" , "13.0" , '%'));
         ASSERT_EQUALS("1.3"  , MathLib::calculate("5.3"  , "2.0" , '%'));
         ASSERT_EQUALS("1.7"  , MathLib::calculate("18.5" , "4.2" , '%'));
+        ASSERT_THROW(MathLib::calculate("123", "0", '%'), InternalError); // throw
+        MathLib::calculate("123", "0.0", '%'); // don't throw
     }
 
     void convert() const {