diff --git a/lib/valueflow.cpp b/lib/valueflow.cpp
index 1576bb448..b43e6cd27 100644
--- a/lib/valueflow.cpp
+++ b/lib/valueflow.cpp
@@ -2497,7 +2497,7 @@ static void valueFlowFunctionReturn(TokenList *tokenlist, ErrorLogger *errorLogg
 
         // Arguments..
         std::vector<MathLib::bigint> parvalues;
-        {
+        if (tok->astOperand2()) {
             const Token *partok = tok->astOperand2();
             while (partok && partok->str() == "," && constval(partok->astOperand2()))
                 partok = partok->astOperand1();
@@ -2517,7 +2517,7 @@ static void valueFlowFunctionReturn(TokenList *tokenlist, ErrorLogger *errorLogg
         const Function * const function = tok->astOperand1()->function();
         const Scope * const functionScope = function->functionScope;
         if (!functionScope || !Token::simpleMatch(functionScope->classStart, "{ return")) {
-            if (functionScope && settings->debugwarnings)
+            if (functionScope && settings->debugwarnings && Token::findsimplematch(functionScope->classStart, "return", functionScope->classEnd))
                 bailout(tokenlist, errorLogger, tok, "function return; nontrivial function body");
             continue;
         }
@@ -2533,7 +2533,7 @@ static void valueFlowFunctionReturn(TokenList *tokenlist, ErrorLogger *errorLogg
             }
             programMemory.setIntValue(arg->declarationId(), parvalues[i]);
         }
-        if (programMemory.empty())
+        if (programMemory.empty() && !parvalues.empty())
             continue;
 
         // Determine return value of subfunction..
@@ -2543,8 +2543,13 @@ static void valueFlowFunctionReturn(TokenList *tokenlist, ErrorLogger *errorLogg
                 &programMemory,
                 &result,
                 &error);
-        if (!error)
-            setTokenValue(tok, ValueFlow::Value(result));
+        if (!error) {
+            ValueFlow::Value v(result);
+            if (functionScope->classStart->next()->astOperand1()->hasKnownIntValue())
+                v.setKnown();
+            // TODO: Known input parameters => known return value
+            setTokenValue(tok, v);
+        }
     }
 }
 
diff --git a/test/testvalueflow.cpp b/test/testvalueflow.cpp
index f396acf56..ae4e2eacf 100644
--- a/test/testvalueflow.cpp
+++ b/test/testvalueflow.cpp
@@ -1761,7 +1761,7 @@ private:
     void valueFlowFunctionReturn() {
         const char *code;
 
-        code = "void f1(int x) {\n"
+        code = "int f1(int x) {\n"
                "  return x+1;\n"
                "}\n"
                "void f2() {\n"
@@ -1769,13 +1769,17 @@ private:
                "}";
         ASSERT_EQUALS(7, valueOfTok(code, "-").intvalue);
 
-        code = "void add(int x, int y) {\n"
+        code = "int add(int x, int y) {\n"
                "  return x+y;\n"
                "}\n"
                "void f2() {\n"
                "    x = 1 * add(10+1,4);\n"
                "}";
         ASSERT_EQUALS(15, valueOfTok(code, "*").intvalue);
+
+        code = "int one() { return 1; }\n"
+               "void f() { x = 1 * one(); }";
+        ASSERT_EQUALS(1, valueOfTok(code, "*").intvalue);
     }
 
     void valueFlowFunctionDefaultParameter() {