diff --git a/lib/tokenize.cpp b/lib/tokenize.cpp
index 9d46147d0..cef06fbcb 100644
--- a/lib/tokenize.cpp
+++ b/lib/tokenize.cpp
@@ -8247,7 +8247,11 @@ void Tokenizer::cppcheckError(const Token *tok) const
                 "Analysis failed. If the code is valid then please report this failure.");
 }
 
-
+// ------------------------------------------------------
+// Simplify math functions.
+// It simplifies following functions: atol(),abs(),fabs()
+// labs(),llabs() in the tokenlist.
+// ------------------------------------------------------
 void Tokenizer::simplifyMathFunctions()
 {
     for (Token *tok = list.front(); tok; tok = tok->next()) {
@@ -8272,6 +8276,26 @@ void Tokenizer::simplifyMathFunctions()
             // Convert string into a number
             tok->str(MathLib::longToString(MathLib::toLongNumber(tok->strValue())));
 
+            // Delete remaining )
+            tok->deleteNext();
+        } else if (Token::Match(tok, "abs|fabs|labs|llabs ( %num% )")) {
+
+            if (tok->previous() &&
+                Token::simpleMatch(tok->tokAt(-2), "std ::")) {
+                // Delete "std ::"
+                tok = tok->tokAt(-2);
+                tok->deleteNext();
+                tok->deleteThis();
+            }
+
+            // Delete abs (
+            tok->deleteNext();
+            tok->deleteThis();
+            std::string strNumber(tok->str());
+            if (!strNumber.empty() && strNumber[0] == '-')
+                strNumber = strNumber.substr(1);
+            // insert result into token list
+            tok->str(strNumber);
             // Delete remaining )
             tok->deleteNext();
         }
diff --git a/test/testtokenize.cpp b/test/testtokenize.cpp
index 22ec7f348..72cb3a813 100644
--- a/test/testtokenize.cpp
+++ b/test/testtokenize.cpp
@@ -496,6 +496,8 @@ private:
         TEST_CASE(platformWin32AStringCat); // ticket #5015
         TEST_CASE(platformWin32WStringCat); // ticket #5015
 
+        TEST_CASE(simplifyMathFunctions); // ticket #5031
+
         TEST_CASE(simplifyMathExpressions); //ticket #1620
 
         // AST data
@@ -8276,6 +8278,46 @@ private:
         ASSERT_EQUALS(expected, tokenizeAndStringify(code, true, true, Settings::Win32W));
     }
 
+    void simplifyMathFunctions() { //#5031
+        const char code1[] = "void foo() {\n"
+                             "    std::cout<<std::abs(0);\n"    // in std:: namespeace
+                             "    std::cout<<std::fabs(0.0);\n" // in std:: namespeace
+                             "    std::cout<<abs(0);\n"
+                             "    std::cout<<fabs(0.0);\n"
+                             "    std::cout<<labs(0);\n"
+                             "    std::cout<<llabs(0);\n"
+                             "    std::cout<<std::abs(-1);\n"    // in std:: namespeace
+                             "    std::cout<<std::fabs(-1.0);\n" // in std:: namespeace
+                             "    std::cout<<abs(-1);\n"
+                             "    std::cout<<fabs(-1.0);\n"
+                             "    std::cout<<labs(-1);\n"
+                             "    std::cout<<llabs(-1);\n"
+                             "    std::cout<<atol(\"1\");\n"
+                             "}";
+        const char expected1[] = "void foo ( ) {\n"
+                                 "std :: cout << 0 ;\n"
+                                 "std :: cout << 0.0 ;\n"
+                                 "std :: cout << 0 ;\n"
+                                 "std :: cout << 0.0 ;\n"
+                                 "std :: cout << 0 ;\n"
+                                 "std :: cout << 0 ;\n"
+                                 "std :: cout << 1 ;\n"
+                                 "std :: cout << 1.0 ;\n"
+                                 "std :: cout << 1 ;\n"
+                                 "std :: cout << 1.0 ;\n"
+                                 "std :: cout << 1 ;\n"
+                                 "std :: cout << 1 ;\n"
+                                 "std :: cout << 1 ;\n"
+                                 "}";
+        ASSERT_EQUALS(expected1, tokenizeAndStringify(code1));
+
+        // testcase from ticket #5031
+        const char code2[]     = "extern int a; void f(){printf(\"%i\", abs(--a));}\n";
+        const char expected2[] = "extern int a ; void f ( ) { printf ( \"%i\" , abs ( -- a ) ) ; }";
+        ASSERT_EQUALS(expected2, tokenizeAndStringify(code2));
+    }
+
+
     void simplifyMathExpressions() {//#1620
         const char code1[] = "void foo() {\n"
                              "    std::cout<<sin(0);\n"